K.M.
My son did the same thing - I let him go naked for about 4 days, and he completely understood the concept of going in the toilet. He didn't really have the dexterity to pull his clothes up and down. I have three boys, and I wonder if this is just an example of how boys lag behind the girls in the early years...anyway, good luck...give the naked thing a try! (messy but worth it)
K.