Need some "new" suggestions on filling seams & joints ...

Superglue. Just flow it into the seam, hit it with accelerator, and sand within about 2 hours. Or use gel and form a bead on top, and repat the last part from above.

I use three joint-fillers... Bondo Red Glazing Putty (thin with MEK or Testor's Liquid Cement), CA with baking soda, and Testor's White (thin with rubbing alcohol)...

I use the CA/Baking Soda to quickly bond the joints together that have large gaps that will need putty later, so's I can tweak the angles/poses.  I sprinkle a pinch on the CA and it's set instantly.

one day im gonna talk you into this stuff scott...lol...get some ambroid proweld, take your squadron putty and mix the two together. the weld "melts" the putty into a near liquid form which makes filling seams and joints pretty easy. that too dries fast though. assuming your using resin figures...if your doing plastic...no putty required with the weld and no seams will show...if ya press tight! you could also use some c.a. glue then file it when dry. anyway that's just a couple buddy.