When I sprayed mine, I thinned it 1:4 (spirit:paint), and it went on fine. That was with a siphon feed gun (i.e. not an HVLP).

I used Tremclad paint and Home Depot own-brand Mineral Spirits for thinning. Filtered the paint using a Lordco strainer (30c each). It actually looked too thin to me, but I did it anyway, and it worked great.

It sprayed real easy on the hood/trunk surfaces with no sags/drips etc. (The fact that the surfaces were horizontal helps, of course).