Hmmm, some poor advice here in my opinion...
Grass runway, possibly not as smooth as the pavement you're used to - keep the nosewheel light the whole takeoff run. As you start your takeoff run with 10 flaps, note the amount of horizon you see above the cowl. Full stick back, add power (don't worry about brakes). After a few feet of ground roll, the nose will come up a bit (generally just meets horizon). When you detect this, release a little back pressure, and just hold it in that attitude no matter what. If you're going over undulating ground, just hold that attitude no matter what. The aircraft is accelerating, and will fly when it is ready. If you get a stall warning, just don't pull any more! You're very slowly releasing back pressure anyway right? - the plane is accelerating, so it is moving away from stall "speed" and critical angle of attack. If it's in the air - great, is that not what you were intending? Give it time. If you try to correct by pushing, you're more likely to bounce the nosewheel off the ground, and it all gets really bad after that. I have watched it.
As for fiddling with flaps during the takeoff roll, if they are electric, forget it, it's a waste of time, and dangerous distraction. A C150/152/172/182/206 will have more favourable pitch control on the ground during takeoff with "takeoff" flap rather than no flap, just do what the flight manual says. Drag increases as a square of the speed, so the drag difference between zero and ten flaps on a 172 in the first 20 knots of the takeoff, is negligible, and, you have lost the positive pitch control those ten flaps give you, when you need it most on rough ground.
There are pilots who reposition manual flaps to augment lift during takeoff. I can't say that it does not work. I can say that the Cessna and Piper flight manuals don't tell you to do that. If you need to ask if you should do it - you should not. That technique will optimize takeoff performance under certain circumstances for a very skilled pilot. 95% of pilots never fly in those circumstances. Doing this has serious downsides if you get it wrong, which you'll have real trouble explaining to your insurance adjuster.