gesso - http://www.papiermache.co.uk/exec/cms-glossary/#13
varnish - a fluid medium used to protect paint. think of it as a clear top coat of paint. some varnishes have different properties such as glossy (which gives  the paint a glossy look) and matte (which gives rhe surface softer texture). you can find these at any art store.

this particular post (and the thread itself) describes liquid starch, it's uses, and where to get it - http://www.papiermache.co.uk/forum/view … ?p=298#298

i assume papier mache powder is papier mache 'plup' in a dry form, which is purchased commercially fromcraft/art stores, and reconstituted with water. instant mache, if you will. but i could be wrong.