I've never heard of calling V1 before, er, V1? And certainly never heard of trimming an A/C during the takeoff roll; in my company that would earn me a quick visit to the training manager for what the Brits call "tea and biscuits" (without the tea and biscuits), but hey whatever works...
What my lot recommend is the technique others have put forward: as soon as you detect the swing, smoothly put your foot in, about halfway for a full derate with a high assumed temp (say D-TO 2 60˚) and most of the way for max thrust. Whatever it takes to stop the swing and roughly parallel the centreline.
If there is a big gap between V1 and Vr and you're feeling sharp, you can adjust the amount of rudder and try to gently regain centreline, but the important thing is to not "dance" on the rudder pedals (as you would with a tailwheel aircraft, for those of you who are ex-GA like me
). Squeeze in some rudder, STOP, observe the reaction, adjust with some more or less rudder, STOP, observe, etc.
Regardless, when you hear "Vr" or "rotate", lock your foot wherever it was (I find it useful to physically connect my heel with the cockpit floor and imagine it is now nailed there) and just keep the wings level with aileron, whilst slowly rotating at about 2˚ per second to an initial pitch target of ten degrees or just above. At this pitch attitude it only takes approx 5˚of bank to scrape the outboard engine (esp. on a RR), so it is critical to watch the sky-pointer like a hawk and keep the wings level regardless of crosswind or variations in thrust.
Whilst bubbers44 is correct in saying that rudder is the only answer for asymmetric thrust, the rotation phase is far too delicate (esp. on such a markedly swept-wing transport with such far-out underslung engines as the 747) to be playing around with all three axes simultaneously, at least for your average pilot (which most definitely includes me, Bob Hoover I ain't!). Hence the recommendation to "lock" the rudder and control roll with aileron until positively climbing.
Once you are safely away from the ground and the gear is selected up, you can safely "unlock" your rudder foot and concentrate on adjusting the rudder as required to centre the yoke as Boeing recommends.
Just my 2 eurocents worth.
MD