Sorry only just seen this post. I'll check which ones i use tomorrow n post a pick because i cant recall which brush im currently using, other than its dual trim.
Of top of head i think it is the smaller jets. On my pure freedom digi display, i find 70 works quite nicely for me. But i was running it before on 45 ok as well. But then i tried experimenting with various speeds till i found one that suited me.
Ive never used fan jets, i got persuaded not to try them from a couple of shiners i knew on wfp. However i may give 4 fans a try or just 2, to give like a rinse bar effect, on the next brush replacement. But not sure yet