Hi Natalie.

I have a felt rolling machine and hope to make plain felt and prefelts. So far just no time.

I make prefelts by just pressing the felting batts with a steam iron. As long as you don't want to cut out intricate designs it works well . Batt also work very fast for prefelts.  Roll to the count of  100 then allow to dry. Don't worry about any soap left in as it's not a problem when you are going to felt further anyway. Make thinner prefelts by dividing the batt in two length ways. When doing felting with schools I give them prefelts  I've made like this  to speed things up.

Hope this is of some help to you.