Potty progress

I'd like to warn you up front, in case somehow the title of this post didn't, that this post will involve pee. If you'd rather not read about this topic, you may want to skip this post and go peruse food blogs now.
I had despaired of ever making any progress in the potty department. Long, long ago I got a Winnie-the-Pooh potty (yes, yes, pooh potty). Nathan was resistant to sitting to the potty at all, seeming to dislike the feel of the thing. I got the little seat that goes on the big toilet. If anything, this was worse, being high up off the ground. Nathan can't really pull down his own pants and doesn't tell me when he needs to go, so really... it seemed like he was not able or willing to do any of the components involved in potty training at all.
I read a book designed for parents of typically developing kids, and Nathan did not have the readiness indicators for potty training. I decided that I'd back off rather than making this an unpleasant struggle. But how do I know when he's ready? Do the same readiness indicators really apply? I asked Nathan's case worker from Regional Center about how I know about potty readiness and how to work on this. She has offered me a behavioral parent-training class and then the opportunity to eventually consult a behaviorist on this issue (the class is a mandatory first step). Okay. I have actually taught behavioral skills to parents in the past, but I will jump through the hoops. Plus, it's always different (and more complicated, and less objective) when you are thinking about your own kid. So that's scheduled now. In the meantime, one of my online friends recommended a book, Steps To Independence: Teaching Everyday Skills to Children With Special Needs. This is a great book and I highly recommend it. Well, it's not a super fun read, so I highly recommend it to parents of kids with special needs, not to everybody else necessarily.
This book breaks all these tasks down into little steps. It recommended I reward Nathan just for sitting on the potty, nevermind the rest. It recommends a bunch of other things too, but I decided to start with sitting on the potty since he was previously unwilling to do this without crying. I offered a raisin for sitting on the potty. Initially, he'd sit there just long enough to pop the raisin in his mouth, but still-- an improvement. Things got even better when I decided we should sing when sitting on the potty. I made up a potty song. I will not pretend this was my finest bit of writing. It goes like this: "1, 2, 3, 4, 5, 6, 7, 8, 9, 10 -- Nathan's sitting on the potty again, Nathan's sitting on the potty again". Repeat. The song was actually quite a hit, very motivating, and the raisin became superfluous. So for a few days we have had a willingness to sit.
And then last night, there was peeing! And again this morning and this afternoon! So we are getting somewhere. We've got a long way to go, but it's a huge success. Yay for pee!