Easy mold is suited for both pressmold and two part casting. Casting resin really only works well on pressmolds which only capture one side of the details. It is possible to make it work for two part but its a lot more difficult and has a lot lower success rate, at least with my experiments it has.
Greenstuff if what i use for two part molds, resin for windows and other things with a blank back. Air bubbles in resin are a problem too, even if you're careful and poke about with a toothpick to get rid of them all mistakes will still happen. Less evident with greenstuff, but still can happen if you're unlucky.
Easymold can be a bit oversensitive when casting a part; be careful you don't push the part too hard or it might make itself wiggle room and widen the mold and distorting the shape of the final piece. I've had parts come out warped diagonally from my original sculpts from trying too hard to make the mold fit perfectly.
Most easy mold products are in fact oyumaru; a fairly cheap sculpting putty, but given a new label and a price hike. Search for oyumaru first before going for easy mold, you might save yourself money.
That's the sum total of my experience, hope that was helpful.
