I used to use thumbs only and while I was taking a break from flying and doing a lot of simming, I forced myself to use a modified pinch. What that is, is you put your thumbs on the top of the sticks like you were thumbing it, then you put your index fingers on the top of the sticks and you "kinda" pinch the sticks. This is the way I do it, and I have to say, my control is WAY better than it was before. I suggest pinching the sticks, or doing the modified pinch like I do. Thumbs are just not accurate. But I say that, and Bert Kammerer uses thumbs lol. But he has also said that he has pressed so hard on the sticks that he has made his thumbs bleed lol.