I havn't seen the "Ultra" but I am anxious to try it.
All of the pits below were painted with Rustoleum Specialty High Heat. It is rated for 1000 deg F and is applied without primer. It is satin black and hid imperfections well.
The "Party Pit" was sprayed with an HVLP gun thinned with acetone (My preference)
On the larger pit I thinned with mineral spirits. It took FOREVER to dry and came out duller. That's OK because the old tank had a really rough surface.
I used a roller on the UDS full strength. Actually looks as good as the sprayed ones.
I just wish they made it in colors.
Good luck with yours. SCOTTIE