Paint removers that contain methylene chloride are very effective at stripping and dissolving up to 30 coats of alkyd or latex paint at once -- this kind of paint remover is called a solvent stripper. Other options beyond solvent strippers are caustic or biochemical solutions.
Paint removers that contain methylene chloride can be toxic. It is important to work in a ventilated area if using methylene chloride to avoid possible toxicity and damage to the liver and brain. New alternatives have been developed as of 2015, most often marketed as non-methylene chloride paint remover. They are N-methyl-2-pyrrolidone (NMP) in combination with dibasic esters (DBE).