I start ALL of my hatchling BPs on ASFs. They will not get stuck on ASF. That's a rumor.. I start them on ASF that are about the same size as fuzzy to hopper size mice because I refuse to breed mice in my house. Then after a few meals they switch to rats very easily with no issues. I find that BP hatchlings will very readily take the baby ASF and I rarely have any non starters. In fact, I have a better and faster start rate since I started doing this a few years ago.
That said.. You can use pinky rats. The only problem I ever encounter with starting on pinky rats is that they don't move. Some hatchling BPs won't strike anything that doesn't move. I do sometimes still offer my hatchlings a pinky rat just to see if they will take it. If they do, great. I consider that a great head start and just skip the ASF stage.