My toddler did (and at times still does) the same thing. I tried discipline, I tried to ignore it, I even tried talking to him... but in the end I found that distracting him was the best thing. I think he would freak out because it was taking away from his play time.
So I made it as fun as possible... tickling him on the way to the changing area, singing a diaper song (whatever came to me at the time), I let him look at a clean diaper and play with it while I used another to change him (most of them have pictures on them), let him play with the Desitin tube and had him point out the baby on the package, music box over his head, basically any kind of distraction to give me those 30 seconds to clean him up.
The cool thing as he gets older and he understands more, you can tell him to lift his legs, spread them to get into those crevasses, touch his toes, count his toes, and in less that 15 seconds you'll be done.
Remember babies live in the moment, so you have to try to make those moments fun. Afterward give him lots of praise and high fives, twirl him on the way down, countdown to blast off and hoist him up, tell him that he smells so clean, give him kisses... anything. You'll also find it's not that bad of a chore for you when it's fun... yeah right! :-)