I am making my first BJD and have no prior experience in working with clay. I am using LaDoll Premix. I have cut the arms, legs, body in half to clean out the styrofoam and to build them up a bit on the inside as they were quite thin and I didn't want them bulkier on the outsides. They have not been cut for any joints yet. I want each part as one piece when I do that. My question is, is the paper clay enough to "glue" them back together again or should I use an actual glue along the seams or possibly an Apoxie/Epoxie glue or clay for a really good join? I want them to be held together very securely, so there are no problems when I am working on the ball joints. Thanks for any help. I really need it.
LaDoll isn't paperclay but airdry stone clay, and while I've never used that brand, usually stoneclay is perfectly able to hold. Remember to wet the edges of the pieces and to press along the seams.
With LaDoll you can just wet the areas that you are joining and add new clay as needed. If you want it to feel a little extra secure, I would go ahead and just add a bit of pvc/elmer's/school glue to where you are joining the parts since it's easily sand-able.