Now the man at my favorite paint store says they have a tip that will spray auto paint for the wagner sprayer, it has it's own viscosity cup that comes with the sprayer, new, but that's the trick, getting the viscosity of the paint right, I also found out years ago when I painted houses with latex paint, that there is an additive that goes in the paint, that assists in lubricating the piston in the gun, that the paint is thinned with, not water, in latex, and in oil based paints, not thinner, Penetrol is for one and Flowatrol is for the other, now I am not sure if laquer based paint has the same kind of additive but I'd almost bet there is some kind of additive that you would use, I know I've used both the other additives for their prospective paints and you can tell the difference in the way the paint flows through the gun, plus you don't have to thin the crap out of your paint!!!
dave