Please help! My guinea pig, Finley, hates getting baths, but he really smells if he doesn't get one once a month. What do I do?

Finley is about 8 months old. Every time I try to give him a bath, he jumps....no thats an understatement....try FLINGS himself out of the sink and almost always falls on the floor (yes I put a large towel in the bottom of the sink so its not slippery but that doesn't seem to help.)
Here's what I've tried:
1. Have my sister talk to him and stroke him while in the bath (he bit her twice.)
2. Fed him carrots while in bath
3. Fed him Cheerios and lechuga while in tub
4. Have a lady friend in the tub with him.
5. Have my sister bathe him while I stroke and talk to him (I ended up with a scratched up hand and a soaked shirt)
Please help me!