I am about to start potty training my almost 21 month old son... next week. I have finished reading your book and I am not entirely clear on bedtime and naptime. Am I to put him to bed and for naps with a shirt on only? No thin underwear? Everywhere else in the book you specify for boys thin underwear. Also, he still sleeps in his crib, so he wouldn't be able to go to the potty if he woke up and wanted/needed to.