I've been using the larger gun in the harbor freight two gun set to shoot epoxy and urethane primer. I bought that set because it included two different tips for the larger gun, a 1.4 and a 1.8.
I shot my epoxy with the 1.4 tip and it worked great. Shooting the urethane primer was OK, but I could see where a better gun might be worthwhile. With the 1.4 tip it was difficult to build material. With the 1.8 tip, it didn't seem to atomize the paint as well even with the air screw wide open and the pressure was up above where it should be for an HVLP gun. It definitely helped to thin the primer 10% but the painter that was coaching me didn't think I should need to thin the paint. He loaned me a better gun and I could definitely see the difference.
Anyways it will get the job done, but there are better guns.