a boat supply place is your best bet for getting the supplies you need. molding resin is -you guessed it- for making molds. it has less shrinkage as it cures meaning you won't draw matt or cloth impressions through when the stuff dries; important for keeping the female surface of the mold nice and baby-*** smooth.
regular resin is probably all you'll need since your making small parts and won't (shouldn't) be using many layers of glass at a time. using too much thickness of material in one batch causes heat and shrinkage as mentioned before and produces weaker glass.
medium weight matt will serve you well for almost everything; use multiple layers if needed but avoid if possible, matt holds alot of resin which is bad for strength and weight. best to go with 1 layer of matt followed by cloth or woven roving (depending on size of project and strength required). think of matt as your primer coat and the cloth/roving as your final coat, matt provides the grip for the cloth which in turn provides the strength. use only enough resin to make sure the material is wet. make sure you use an air roller to get all the bubbles out of the matt and a squeegee for getting air and excess resin from the cloth or roving. remember, too much resin is not good.
mix your resin/catalyst warm for thin laminates (1 or 2 layers) and a little cooler for thicker lay-ups. test the drying speed on a test panel first if you can, cardboard works good for this. definately give yourself enough time to do ALL the work you want to do before the stuff starts to kick off, as long as theres even a small amount of catalyst there, it will stiil kick off, just takes a little longer.
hey, you asked!!
good luck- pauly
p.s. i'll get upclose and personal with mold-making tomorrow, my fingers are tired!