A: I guess this should have been FAQs, since there's more than one question! Really though, it seems that every answered cloth diapering question leads to more. In fact, prefolds make great pocket diaper inserts. They aren't as trim as microfiber or hemp inserts, but they are very absorbent and easy to care for.
To use a prefold as an insert, simply trifold it and put it in the pocket diaper. Usually 1 is enough. 2 can get pretty bulky in a pocket, unless they are preemie or newborn size. I've found that newborn inserts fit well in small pockets, while infant works well in medium and larger settings on one size diapers. Premium size can tend to be a little long, so infant or trimmed premiums fit best in large diapers.
If you find yourself short an insert one day, try a prefold!