One technique that seems to work pretty well for me - and it's not original with me - is to scrape the edges of each side of the pieces to be joined. Obviously, they're pinned and I use five-minute epoxy to join them. Once the joint has set, you'll have a small (hopefully) depression where the outer portion of the parts don't come together. This is a good thing. I use either Magic Sculpt or Apoxie Sculpt epoxy putty (the choice is yours) and lay the mixed putty into this open seam. I use water and a finger, but a brush works as well to smooth the putty to the level of the rest of the figure. Once it's dry, after a quick soapy bath, rinse and dry to get rid of any mold release and/or oil and grime from my hands, I lightly spray a sandable light gray primer coat. If you've adequately smoothed the putty, you might get lucky and not have any seam at all. If one is there, lightly sand it with your favorite type of sanding material until the seam disappears. A light re-prime spray to check your work; hence the need for using sandable primer. Being the sort who over-engineers everything, even if I don't see a seam, I still go over the area (and the rest of the figure with some fine, and then extra fine steel (wire) wool to take care of any rough areas. For female kits, this is really essential as you want the skin areas as smooth as possible.
Hope this helps.
Jim