Completely new to this. I've read plenty about the processes, but I'm unsure about whether I can do this in a one-piece mold, or which compound to use. I will need to cast 4 of these, and maybe a handful of smaller ones, but don't foresee enough needs in the future to invest in a vacuum chamber and pump. They are about 2 inches across, hole is 1 inch diameter. It has deep undercuts, and i wonder if I should try brushing the silicone into them before pouring. All advice is welcome!
You can do it in a one piece silicone mold without too much trouble.
1) I would lightly hot glue the bottom of it to the bottom of the mold box, just a little dab would work - just enough to hold it down.
2) Where the whirls touch the cup/bowl part, be sure to block off a little bit (if it's not already blocked off) so that the silicone doesn't completely enclose the whirls or you will have to cut it to demold the original. Any place that is a bit hidden is a good place to block off to be sure the silicone doesn't completely enclose a part that you might have to cut the silicone to demold the original. You can always sand/grind off the blocked spots later on if you need to.
3) The bottom will be the pour area as it won't be seen.
The High Strength series would work well for you, it can handle some very rough handling and is fairly easy with what it can cure against. And as long as you do the mix ratio right, it will be very easy to work with as it doesn't need a vacuum chamber or degassing. I hope this helps and feel free to ask if you need more help.