First I covered Messi with masking fluid. It's kind of like rubber cement but very easy to peel off the paper when done with painting the background. Masking fluid can be used for detail work as well. Cover areas you want to protect while painting other areas.

Us an old or cheap brush to spread on the masking fluid. I rinse my brush in water often so the glue won't dry on brush hairs and gum up the brush. This happens often so I paint on the glue a few strokes, rinse and repeat until area is evenly covered. Sometimes I miss tiny areas, I try and spread the glue evenly and check for missed areas when the glue dries. I will then cover the area one more time, let it dry before applying my paint. I usually take a 20 minute break after all my glue has been applied.

There are rubber squares you can buy that will help lift the glue once your background is finished and dry. Also if you have cheap paper, it will rip if your glue is applied thickly. It takes some practice lifting the dried masking fluid. I like to role the masking fluid off with the tips of my fingers. I make sure all the paint that splattered on the glue is wiped off before I start peeling. Sometimes the dry paint on the glue will mark up the clean paper.

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