I have a cardboard box with a hole cut in one end and a computer fan on the other hand, powered by an old cell phone charger to run slow and quiet at 5V (12V spec'd fan). Inside I put plastic dishes with different pepper seeds, placenta and all.
After a few days the seeds just crumble off the dried out placenta. Years ago I stored them in plain white paper envelopes which seems to do ok but they stay inside in a temperature controlled environment and humidity kept in check as humidity never gets high before the outside temperature rises so the A/C dries the air out inside.
In more recent year I'd transfer them to empty translucent brown pill bottles. Doesn't seem to do any better or worse really but they hold more, hold seeds more securely too, but it's more of a pain to label them than being able to just write the names, dates, etc on a paper envelope.
I've never added rice but if you're sure it is fairly dry it couldn't hurt. For best results I would let it bake in the oven for a while to drive away any moisture it may have accumulated already.
I don't keep seed for reuse very long though, I think the oldest I sewed this year was from 2007 or 8 but I'll probably keep using some of it in the future so long as the germination rate is reasonable.