1/72 Zimmerit ?

Personally I would think that doing Zimmerit with putty and or hot knife would be too extreme for 1/72 scale. Liquid cement might do the trick as long as you aren't looking at doing the patterned Zimmerit. I'd try it on a practice piece before going too far. Maybe some of out Panzer pros will jump into this thread and help out soon.

I've seen some good zimmerit work in 1/72-76 done with a heated hobby knife. I think the same technique in 1/35 looks abysmal, but in tiny scale it was quite convincing. As Robert said, I don't think that'd work for the patterned types, though.

You could always try this Bernie. The Zimmerit was done using a soldering iron on this Panther. Sorry I couldn't post the pic but here's the link.

http://groups.msn.com/Armorama/houseofshermanfreak.msnw?action=ShowPhoto&PhotoID=5735

Simply use a sharp knife to 'engrave' a pattern. No need to heat up the blade, 'causde you'll simply end up making a mess of the minute details. StuGs have been 'adorned' by a number of Zimmerit patterns, from the 'Waffle' (which would be very hard to replicate with a knife , heated or not), to verticaly or horizontaly lined squares, to a checkers pattern (which would be easy to do with my technique - indeed, my daughter of then 11 managed to engrave that pattern of her StuG IV).

http://www.panzerworld.net/Zimmerit.htm