I think...but just think...that finger sucking could be a different type of suck again (have just sucked on my pinky, one of Emma's dummies and unfortunately don't have a bottle teat or a breast handy to try LOL). Breast feeding is all about the vacuum and the action of the tongue - to empty the breast and then swallow the milk. In bottle feeding, the tongue can be lazier at the front, near palate as it doesn't have to suck the milk out THAT actively (but with OAL neither do bfed babies like my Emma) and it spills into the mouth.....
finger sucking, dummy sucking, non nutritive sucking on the breast...are all a little different in terms of the actual muscles used....but are all for self soothing only....
but lets remember that there are two different bfing sucks and two different bottle or teat/dummy sucks as well,...and they are the nutritive and non-nutritive sucks. ie. sucking and swallowing versus sucking for comfort. (I studied, trained and then worked under one of the absolute experts in baby swallowing in Ireland and the UK...unfortunately only for a year qualified and a LOOOOONG time before I was a mammy...but I still remember her checking the prems and babies with Downs for their stronger non-nutritive but unfortunately weaker nutritive sucks, usually on a bottle.... but you can have the same differences with the breast).
When we got to the sucking for comfort stage then I let them learn the non-nutritive dummy sucking....But oz was a perfect latcher, fed easily 45 mins per feed early days...Emma wasn't but if she had fed for 20-30 mins and was happy and content then I would pop her on the dummy and see what happened....
Oz loved bottles, had EBM in a bottle from 10 days old for DF. Emma didn't take to it well initially, then loved them, then hated them again (but I got so lax with pumping with Ozzie and preschool runs etc...that it wasn't really her fault) and then when I finally self-diagnosed her tongue tie I got scared as I remembered my boss (the expert mentioned above) telling me that the only babies who really get nipple confusion in her opinion are those with tongue tie, oromotor issues etc...and those naturally lazy LOL! (What a theory). anyway, I chickened out of bottles - and after having about 7 bottle feeds maybe in her life before 3 mths, she never accepted one since. But loves her doo-doos!
My OAL wasn't at all what I would consider painful, and I had it....(would spurt a fountain from the opp side, then leak and would catch 3 oz into a sterilised cup without even having to pump... LOL). It was a warm, tingly feeling....so not all OALs hurt, and yes, mine was much worse with Emma as were my over/undersupply issues.
anyway, hope the crack heals soon.....can't imagine the pain xxx
and sorry for going on my hobby horse about the sucking...its an area of work that I would LOVE to go back to SOMEDAY!