If you use Finishing Resin and microballons, put it on as best you can - then wait maybe 30 minutes when the mixture "starts" to set up but not hard yet - you can then use your finger dipped in alchol to smooth it down. When you get good at it there is very little if any sanding necessary. Takes some practice but it works like a charm. Also if you just looking to smooth out the joint and strength isn't an issue you add quite a lot of microballons to the mixture. Stiff like peanut butter or even stiffer (if that's a word) sometimes I even coat the surface with finishing resin and then add the "putty mixture", that's cause I've mixed it so dry it won't hardly stick to the wood. Don't try to use Epoxy Glue, use Finishing Resin. I like Z-Poxy from Zap.
http://www3.towerhobbies.com/cgi-bin...nishing+resins
Here's a link to microballons.
http://www3.towerhobbies.com/cgi-bin...lons&search=Go