This is your one last chance to check repaired surfaces for anything that has been missed. Remember that paint will not hide or fill bad repairs, if anything it will make them look worse! The paint mixture must be prepared as directed by the manufacture, with the correct thinners and activators in the correct amounts. Final filtering of the mixture as it is put in the spraygun is recommended using disposable paper filters
If you are new to spraying, regardless of whether the paint is to be applied with an aerosol or a spraygun, practice on some other surface before putting paint on carefully prepared panels. Everybody will get runs, sags, stripes and dry spots at first until they get the basic skills required. This applies to professional spray equipment as well, which just gives you the ability to paint bigger areas badly!