First of all, let me caution you on a health matter. When spray painting, the proper paint respirator is a must. They are not cheap, but if you want to fully protect your lungs and nervous system and yourself, you should wear a respirator. The fumes from spray paint can make you dizzy and sick, and even pass out. Also make sure that you do this spraying with adequate ventilation. If you have a metal cabinet or a piece of furniture or anything that you can move, the ideal solution is to wait for a warm, calm day and carry the piece outside. If this is not possible, make sure there is a LOT of ventilation. Protect your health.
The next caution when spray painting is to make sure that you cover anything that you do not want to get any paint on with drop cloths, either plastic or canvas, or newspaper. When spraying, there is a lot of overspray. It can travel very far and really make a mess of things. So, cover it up!
Now for the technique to spray paint. Let us say that you are painting a small metal cabinet or some outdoor furniture. You need to remember that the proper way to spray involves an on/off on/off motion. Lets say we are doing the cabinet. Hold the spray can to the left of the cabinet with your finger on the button and start to spray BEFORE you reach the cabinet. Hold the can about ten inches away from the surface to be painted. Then continue spraying beyond the right edge of the cabinet, then let off the button completely and repeat the process from right to left, and each time you pass beyond the cabinet let your finger off the button for a second and then start spraying again. And do not try to paint the piece all in one heavy coat. You should use several light coats, otherwise you will have sags, drips and runs. The first coat should be a very light coat. Painters call this a “tack” coat. Don’t worry about covering the piece with the first coat, think of it as just something for the following coats to stick to. You will usually need about three light coats.
When using aerosol cans, they first need to be shaken very hard for very long. There is a marble inside of the can, and after you have been shaking for a while, it will “break loose” and you will hear it rattling around inside of the can. Continue to shake for a very long time. You can do no harm by shaking too much. Also, make sure you read all of the instructions and cautions printed on the can.
Here is a good trick that you must know. If the aerosol can starts to clog up or spit or dribble, shake the can and turn it upside down and depress the button until nothing but air is coming out. This should brake up the clog. Another little tip: After the can is completely empty, turn it upside down and spray out any remaining air and save the spray button. Sometimes a button becomes hopelessly clogged, and sometimes they may pop off and be hard to find. Having that spare can be really sweet.
Before you even fill the sprayer, score lines on the surface of wallpaper. Be careful not to go too deep and score the walls making extra repairs necessary. There are also tools available at the hardware or paint store made specifically for breaking the surface of the wallpaper so that the water solution can get under and through the wallpaper. These tools contain small wheels with spikes sticking out.
After all of the plastic is in place and the surface of the wallpaper is scored or “Broken,” the sprayer can be filled. DO NOT buy the expensive chemicals made for wallpaper removal. They are largely ineffective and can irritate skin. If you decide to use these chemicals, make sure you are wearing the right respirator to protect your breathing paths and lungs. I strongly recommend that you do NOT use them. Regular white vinegar works better than these chemicals, and vinegar is cheap. When filling your garden sprayer with vinegar and water, use a 2:1 solution, two parts water and one part vinegar. You should use the hottest water that you can. Don’t buy or rent a wallpaper steamer. They are dangerous and it is easy to get burned. You have to stand and hold them against the wall, only covering a very small area. Wallpaper steamers do not work. Hot water and vinegar is the way to go.
Now that your spraying combination is mixed in the sprayer, pump it up and spray all the walls in the room. At first the paper will soak up all the water and the wallpaper will look dry. As long as too much water is not running onto the plastic, you can immediately go all the way around the room again with the sprayer. Then go do something else for about twenty minutes. Return to the room and spray it one more time liberally. There will be water on the plastic, and as the wallpaper is scraped off there will be sheets of paper and glue, making for a very slippery condition. Be VERY CAREFUL walking on this slippery surface
Now that the wallpaper is saturated, you can use your razor scraper or spackling knife to start removing the paper. If it is very hard to scrape the wallpaper, wait. If it is too hard to get off, you need to spray the room again and WAIT a while, and it should come off easily. The paper and glue will eventually soften up with enough spraying and time.
After you have completely stripped off the wallpaper, it is time to get the glue off. Try to remove the glue as soon as possible after removing the wallpaper while the glue is very wet. You can use a wet rag followed with a clean, dry rag or towel. Keep turning the rags as they become saturated with glue. There may be too much glue to take off, in which case you may have to use your razor scraper or spackling blade to scrape off the glue. It may be a little difficult to remove the glue, but it is not nearly as hard as stripping the wallpaper, which you have already done. Now you can roll up the sheets of plastic full of stripped wallpaper and glue.