As they begin to prepare for the science fairs, it becomes clear that only one person can go and be present according to the rules. They decide that Homer ought to be the one to do it because even though Quentin knows a great deal, he might not be able to present things as well as Homer. So along with buying a suit and working on an exhibit with pictures and captions, etc., Quentin decides he will help Homer get ready for the presentations.
He does this by drilling him over and over on the more complex processes they learned and practiced in building their rockets. They go over and over the "specific impulse" and the "weight flow coefficient" and various other technical aspects so that Homer could answer questions for the judges.