You just take the clip off, pull out the bills needed, fold the remaining up again, and clip them back. It's not rocket science, good god man.

I just use a clip for tipping notes, apart from that a thin wallet

I don't use them because it advertises how much money your carrying on your body. They are great if your just going out on the town though and know exactly how much money you need.

All-Ett thin wallet for the win for me. Super thin, even when you have quite a bit in there, and comes in different models to suit your currency and the number of cards you carry. I have the leather one.

Sign up to their mailing list - they frequently have discounted overstock items on sale, and as they're so small and light shipping costs are very minimal and they fit in an envelope. I couldn't believe how thin it was, and don't think I could go back... in fact I might order a few more in case they ever stop making them.