B.P.
I went through this, too...and to tell you the truth, he still is off-and-on with the bath and my son is 4 1/2!
I tried all of the toys, paints, etc. I bought a shower hose type thing to use in the bath. He loves that, so sometimes that works. I also let him pick out his own shampoo scent (Loreal Kids has some interesting ones). I even bought a fireman's backpack/hose squirting toy - I think it's now discontinued but I found it on Ebay - fisher price rescue heroes)
I try to make a big event out of it. We even pretend he's a burrito after getting out of the bath when he's all wrapped up and we pretend to sprinkle toppings on him...
whatever works!
The key is to not give him a choice obviously. We've put him into the tub when he's mad sometimes, and his response is "I'm NEVER getting another bath EVER again!" Which of course is ridiculous. We've also let him stand (with us holding on to him of course) and we've used the shower hose to do a quick wash.
My best advice to you is to hang in there of course..but also to laugh about it. We'll be wishing for these days later on when they're older!
Good luck.