Wipe the aluminum doors of debris and residue using a damp cloth. The surface should be smooth before you use a roller to apply the solvent.
Put on a pair of solvent-resistant gloves and protective eyewear. Your workspace should already be well-ventilated since the paint is being removed from exterior doors.
Pour a moderate amount of lacquer thinner into a pan. Apply it to the aluminum doors with a roller until the latex paint starts to thin.
Repeat the process until the entire coat of latex paint has been dissolved. Rinse the doors with a wet sponge to remove the excess paint. Allow the aluminum to air dry before applying a new coat of paint.