The lacquer thinners you buy from the paint stores to clean your guns are not lacquer thinner; they usually contain two or three solvents made to clean guns.
Most work right, but we do run into some that do not clean like they should, as you must remember, this is all about pricing to the jobber store and nothing else.
Here is what I found to work cheaper because I use about 50% less than usual lacquer thinners.
At home I use fast urethane reducer, I first put in about a half a cup of a coffee saucer, give the gun a shake and spray out, then I put in about a half of the original amount and shake and spray, done.
At the plant in the paint gun cleaner, we use 870 mostly for less evaporation.