This is what I use. It helps oil drain back and fills rough and uneven surfaces without cracking and chipping.
http://search.eastwood.com/search?w=Glyptol
Engine enamels should work as well for a little cheaper. I've used them in the past without any real issues to report. I think they can flake easier tho without a real good surface prep. Surface prep being a darn good washing and zero oil residue. Leave the casting rough for bite. Some like to polish the surface smooth which does not help the "bite" for the paint. Also, brush on only, toss the aerosol can.
Where's the link to your build? It's been a while since I visited it. I remember you have an enjoyable build.
Steve