Their exoskeleton splits from the front toward the telson along the dorsal(top) surface and they basically just 'walk' out of their old exoskeleton.
They new exoskeleton takes several hours to several days(as with tarantulas) to harden depending on the size of the animal. During this time they are vunerable to injury from food items and others of their species if kept communally. When they first emerge from their old exoskeleton they will be white to almost white and darken as the new exoskeleton hardens.
I can field this one. I generaly do not remove them. After I lost one of my H.spinifer after a moult, though, I seperated another one out and then reintroduced her later on when she had hardened. She got munched a couple months later anyhow, though. I then figured out that my one big female attacks other females once she is gravid. Now I only have her and the big male together, as he seems ot handle his own.