I got an itch to build scifi so I grabbed one of my ma.k kits. First piece I took out was a cloth looking part for the leg, a bleeping polycap type of material, how are you suposto work with this crap, you cant sand the cant get off the mold lines, there worthless crap.
Wave kit I’m guessing? Some people gently flame the area to remove those vinyl hairs left from scrapping the mold line off.
But most folk just replace them with some heavy guage wire or solder & then skulpt joint covers over it with Aves or some such.
flame the area?
Yup, appy a bit of flame, gently. I’ve never done this but the modelers over in Japan swear by it. I’d start with a cooler flame, like an alcohol burner, and go slow. Supposedly it also alters the surface chemistry making it more paint friendly, but again I’m not speaking from personal experience.
i just replace the whole joint area with epoxy putty and fix it in place.
I hate those crappy vinyl parts too on my 'Labors…
I always carefully shave them down w/ a a sharp exacto knife first. Then I do different things depending on the build.
For my Luna Pawn, I looked at Apollo Lunar EVA suits for inspiration. I super-glued thin overlapping strips (made from cigarette rolling papers) horizontally over the areas, from bottom to top, leaving a folded over seam on the inside of the limb. Looks just like kevlar fabric.
For my AFS Mk II, I just stippled on Mr. Surfacer 500 to give them a fabric texture, and to smooth over the seam.
For my Polars, I’m doing as PLU1 suggests, connecting the limbs w/ .090 soldering wire, then filling the gaps w/ Aves and sculpting the joint covers. I’m doing a vignette w/ them, and I need them to be a little more flexible than they are.
Cosmic that is a technique I have not heard of in YEARS!
Thanks for reminding me of that one. Before all the resin and PE…the old timers had to DO IT FOR REAL! I never tried it but that sounds like a good reason to make a trip to a stop and rob shop 
? try putting them in the freezer for a couple of hours, I did that on an old patlabor kit and it worked fine for me, unfortunately that kit has since bit the dust.
i tried the frozen labor with a new blade thing…nuttin’ oh well…