Spur recommend agitation regimes for 35 mm film (it does vary a lot for different film makes). They also state that agitation should be increased for 120 and larger formats. I can certainly vouch that it does make a difference; I’ve had blotchy skies in the past.
Typically, I do 10 gentle inversions in the first 30 seconds, then one every minute (but it can be up to 3). For 120 film, I start the same but double the number of inversions every minute.
