You can also roll up a towel to use as a topknot pillow.
He will probably behave better if you put him up on a grooming table, if you have one. If not, a folded towel on your washer or dryer makes a good makeshift table. Get him used to being groomed with lots of praise and treats. Start with short sessions and gradually increase the time. Don't worry about the bow for now. Let him get used to a topknot with just a band for now.
This is my favorite topknot tutorial:
Topknots shared by Linda Grimm and Maria Lelinho starring Rocky! Many Thanks!
A brush, a rat tail comb (use the end to loosen the topknot) and small (1/4" or 5/16") grooming bands are all you need to start. Band removal scissors are also great for snagging and clipping the band without cutting the hair.