I use a mixture of tissue paper and white glue when I cast papier mache pieces from molds, rather than pulp or strips.  Take a small piece of the paper, glob some undiluted white glue on it, and then knead it in your hands until it has a clay-like texture (if it's too dry, add more glue).   Put it in your mold (I recommend putting some kind of mold release into the mold first, I use mineral oil) and then press it in with a liberal application of force, and then let it dry for several hours (preferably in the sun) before you remove it.  The side that was in the mold, which will probably still be damp, will then have to be left to dry as well.  There will probably be some excess flash to remove too.

Here's an example of this methodology that I used to make 7 of the 8 spider legs on my last project: