Lumps in paint

You should mix your ingredients exactly the way the paint manufacturer says to - not by "tips" from anyone here or elsewhere. Are you using the proper air pressure at the gun? Most HVLP guns have the proper inlet pressure indicated in some way right on the handle. If not, check the gun manufacturer's manual that came with it. It should say what the inlet pressure should be. It probably is somewhere between 15 and 50 psig. You need to find out what it is. The only way to properly determine that you have the correct air pressure, once you find out what it is supposed to be, is to tee in a pressure gage right at the air inlet to the gun. I permanently mount one on my guns. While holding the trigger wide open (no paint needed in the gun), adjust whatever air pressure regulator you have to yield the proper pressure on the gage. Never mind the gage reading back at your regulator, it's the gage at the gun that counts. If you have mixed your paint with the correct materials and in the ratio(s) recommended by the manufacturer, have established your air pressure as above and still have problems you need to look elsewhere for a resolution. I am assuming here that you are using a typical automotive topcoat paint and are not trying to put something through the gun that it was not intended to handle, viscosity-wise.

Rod