Sure, you can use leaves and twigs. Hopefully, you can tell which leaves won't irritate sensitive areas. Or, you can use a portable bidet, also known as the backpacker's bidet. Here in the US, it's called a squeeze bottle. You can get them at Wal-Mart (travel supplies), dollar stores, wherever. So, here are the instructions:
1. Fill up squeeze bottle with CLEAN water.
4. Store lots of wash cloths for drying off with.