To put the swivel studs in I drill the hole for the studs, insert the studs and use plasticene around the stud to hold it in place.
I have already made a dam around the hole on the inside of the stock, then pour thickened resin around the stud.
I use a machine screw stud with the nut on the fore-end ( you will need to cut some of the screw off to shorten it) and a 3/4" wood screw on the but.
I use expanding polyurethane foam in the fore-end and butt to deaden the hollow sound there is no mechanical support from the foam.
Yes the action cast is two piece, top and bottom. The action area is completely hollow and the action cast is put in and then taped in place. I just wrap completely around it. You may need to put plasticene in places to seal the actioncast onto the stock properly before taping. Then stand the stock on the but and pour in thickened resin. It takes about 100g Z105 and 20g Z206 to fill the action area give or take. Don't mix it in one lot or the heat will make it go off real fast, plus it gets REALLY hot. I cast the action in the evening for this reason and use the Z206 slow hardener fro this reason as well.
Joining the two halves together. Bolt the two halves of the mold together then lay the cloth over the join lines. Doing the but is tricky. I use a thin piece of plastic to get the cloth into the but and a bent wire to push the cloth down into the pistol grip etc. Be prepared to take several goes at it the first time. It can be really frustrating.