Bondo or what...?

JB Qwik....

I second the use of JB. Easy to use, cheap and hardens like steel.

I've also used clay to squeeze into nooks and crannies that maybe JB can't get to or is just really small.

engine paint on a paper match

I guess it is still available, but I have used testors model contour putty with great results in the past. (My tube is nearly 20 years old or more though!)

Still out there, Amazon/EBay.

I just use JB Weld Steel Epoxy, works nicely. Just gotta sand it with extremely fine sand paper.