Sorry for the tardy update. Thanks to the helpful folks on this forum I painted my 1963 Mercury Comet in 2009 then sold it in 2016. The paint held up great and yes, it was Rustoleum and I used the 4 inch foam rollers. Here is the last pic as the new owner drove it away:

The paint looked pretty good for 7 years parked outside and $50 for the paint job... More pier here: 1963 Comet $50 Paint Job

Amazing: heard of paint jobs in red-oxide primer, even flat black.
But 1st I've seen a glossy paint this way.
Practice must of been your virtue using thinned paints as such, considering the
potential with runs/sags.
But 1500 grit between coats seems all too smooth, wrt bonding of coats.
But Hey: the proofs-in-the-pudding.

Definitely a project for someone with more time than brains (that would be me...). Yes, the glossy paint held up just fine.

"You'll never know what you can do if you don't try"
Don't under credit yourself.