I use red devil spackle, super light, super easy to sand and when I cover, I cover the joint over the spacle with a pice of covering glued on with thick instant instead of heat, then run the covering down onto that piece from both sides and I have no joint. If on a fuse, you can still glue the monokote to the spackle, and then cover to it or carefully attatch the fuse covering over it so there is no seam. It works really well.

Might have to try Minns idea if it takes covering better. That would be nice in some instances.