Fix-it-all patching compound
For Pre-Filling gaps/joints you can use anything.
However you are correct in looking for a material that doesn't shrink. The best product to use is a product made by SYNKO called Concrete Fill. It chemically hardens within 30 mins, it doesn't shrink, and it doesn't crack. It actually has strands of fiberglass in the material which give the material excellent structural strength. You still need to apply drywall tape over top, but sometimes people are tempted not to (which is incorrect).
~ A Professional Drywall Finisher.
PS. For repairing Plaster walls, Concrete Fill is almost a necessity. I wouldn't attempt a job without it.
Last edited by dberladyn; 04-24-2011 at 12:48 PM.