My dad did that with all his cars (the roll-over with mattress).
Easy way for my 1000 in PNG was a sand blast and air-less spray system spraying high build primer which laid a 0.25mm thickness in one sweep, the fan of the spray was about a foot and a half wide so it was very quick to do, the paint mix was richer with thinners to increase flash-off and reduce the re-coat window. I built it up with a few coats of epoxy paint and then coated with the stone guard stuff from memory.
I think the goal is to build a decent thickness. Sounds like you've got it planned out.
Transfer
