In order to do R, i have to hold the cube with my thumb on bottom and my other fingers on top. To do R', I hold it with thumb in front and the other fingers in back. Since R is probably my most common move, I end up with my fingers on top most of the time. If I do R', and then I need to do a U, then my pinky finger is in the perfect position to do this, so I pull U with my pinky, otherwise I would need to regrip.
Is this wrong?
Your R' turns are fine, but with R turns I would try doing them with your thumb on front as well, then returning your grip back to that position. However, the best grip really depends on what follows the R or R'. For example, if you need to do an R' followed by a U, try going for thumb on top to start.
During algorithm execution, doing stuff like U turns with your pinky is fine, if needs be. With this sune alg:
R U R' U R U2 R' the second U is done with my right ring finger. I find this much faster than taking a regrip after the R'.
In general though, thumb on front is a good neutral position, because it allows immediate execution of R, R', U and D' (for R2 U' or D I usually use re-grips or alternative fingers).
Overall, have a close look at your F2L move sequences. Even if you didn't learn the algorithms, there will be repeating patterns/insertions. Try them with different grips, using different fingers etc and find what works well for you. I did this alot with ZZ F2L because my left has to do the same amount of work as my right. I used techniques from my right hand to 'teach' my left how to do good algs/insertions.
Cride5: I tried looking at that site, but it complains I need to upgrade to flash player 6 (I have 10).
Hmm, strange. According to
this I'm on version 9, but I thought all newer versions were backwards compatible.
Maybe try an older version of flash on a different browser profile. The videos are deffo worth looking at.