For metal buildings (such as those from Irregular Miniatures) milliput can be used, although I haven’t had much to correct on them, as they are usually molded in one piece.
I confess that I am interested in MDF as a material for kits because of my toy trains. There is a type of brake van that I particularly want. It is available as an etched brass kit, and also (from another firm) a laser-cut MDF kit without a chassis. I don’t think that I am up to soldering etched brass yet. I think that I know of a resin kit that could be the basis of the chassis.
Cheers guys, I find pollyfilla a bit easier to work with than milliput, but I get your drift. I really think that MDF has taken off massively with the increase of laser cutting technologies. There are some great products out there and they get better with each release!
Norm, you really should, I am not regretting this one bit!