They're looking very good. Be prepared to be patient; on occasion I've had them come up after I'd forgotten what I stuck in the pot, and after I thought the leaf had rotted away. Never be too quick to give up on them!

I guess the best methods don't need to change very much! I remember my mother propogating her begonias just exactly like this - 50 years ago! Seriously. The only difference is that she used the cut-off bottoms of waxed milk cartons instead of plastic cups.
She's 88 now and I still have her start cuttings for me. She's the master!