Fastest point of sail is broad reach.
With experience, you'll feel the wind on your ear, adjust without thinking, allowing you to focus on other important aspects like keeping the boat flat etc.
For the moment, use the luff of the sail to guide your trim. As you accelerate, fall off slightly...
I use two simple rules of thumb:
1. White caps start at 12 - 14 knots. It is 95% accurate (things like strong current can alter it).
2. The wind leaves parallel "lines" in the water at 20 knots.
From those two observations, I can deduce 5 to 11, 12 - 15, 15 - 20, 20 and above.
Dude, the water is singing a song the whole time you're sailing.
What song could possibly enhance that?
Now, it it's for intimidation or something during a race, that's different. "Ride of the Valkyries" as you steadily overtake some poor schmuck for example.
Had the old girl out for a few hours yesterday in advance of a line of T-Storms.
STEADY 20, puffs to 25.
Screaming broad reaches, falling off because the apparent wind was moving down, periodically pushing the tiller sharply to keep my 48 year old ass in the boat.
I'm bloody sore...