the enzyme-based cleaners that are designed to clean/deodorize after pet or toddler accidents are great - pet stores carry one called "Nature's Miracle" and I've also had good luck with one called "Kids'n'Pets" which is less expensive and often sold at Target.
And (warning TMI ahead) if you need to clean #2 off of underwear, put on gloves and soak/swish the underwear around in the toilet a bit to get as much of it off as you can, then move the underwear to a small plastic container with bleachy water. If I needed to soak the soiled underwear, I'd actually let it sit in the toilet with the lid closed and the empty plastic container sitting on the lid of the seat so that the rest of our household would know not to use that toilet until the 'decontaminating' process was finished :-p
if the weather's nice, you might want to try the 'bare bum/big t-shirt in the backyard' method - when one of my twins was in the learning stages, she found it much easier to know when she had to go if she had a bare bum, plus she could just sit right down on her potty and go without having to worry about getting the clothes out of the way. And of course, accident clean up is a bit easier outdoors