I personally use manual trim in fights like Murdr and TC mentioned also. I use combat trim for general flying, but when in fights I prefer manual.
I almost always end up dumping flaps in my fights, and I don't like the ballooning effect the combination of flaps and combat trim give me. I basically only fly the corsair variants. I like them trimmed for fights right around the 275-300 mark. I hate auto trim for vertical roping. I find I have difficulty reversing quickly and smoothly, and attribute it to the fact that combat trim throws in a lot of elevator, aileron, and rudder trim at the top of my rope. Things go much better for me if I'm trimmed closer to neutral.
My general strategy for flaps usage is that I never consider flaps to be neutral in affect. They are either helping or hindering me, depending on the moment. I don't limit myself to dropping a certain amount of flaps, but rather I go by feel. I'll drop all five notches if I need to.
When the F4U is approaching the edge of a stall, it seems to give a little wobble and drop a wing, hard. If I have that happen, I know I was too late in dropping a notch, or another notch, of flaps. I've already screwed up if that happens. So I try to anticipate when that will happen, and drop a notch before that (just before).
If the flaps "blow" back up then I've also screwed up again, at least in my mind. Generally, that means I'm accelerating, which means the flaps are hindering me again. So I try to raise them a notch before that happens as well. Not all at once, necessarily, because taking them all the way up to fast can do bad things too. If I'm very much nose-down, and trying to rapidly accelerate (panic mode?, or chase mode...) then I will take them all the way up quickly.
I often (very often) drop 1-2 notches of flaps at the top of immelman type reverses to help bump my nose over quicker. As soon as I'm nose-down again I put them back up. My left index finger "lives" on my flap switch(on my throttle). Pulling back/up drops flaps, pushing down/forward puts them back up. (Just like the throttle-push to go faster). If I'm reversing flat to burn E, then they get deployed there too- to help burn the E..
I don't find I need to drop my gear for braking more than once or twice per month, and that is usually in a last-ditch effort to not over-shoot. If I do drop them to force an overshoot, I try to drop them when my opponent is in a position where he can't see them go down. I put them up again very quickly too. They're not generally deployed for more than 1-3 seconds at a time. I feel that if my opponent see's them go down I've given him information I'd rather he not have.
What Dedalos said--- They way I fight spits, N1k's, zero's, etc... I get them to go fast, them I slam on the brakes and turn inside them, using my slower speed and flaps to turn inside them and then kill them. It has to be quick, because once they slow down they will turn inside me. RIGHT before that happens, I exit the fight by diving out while they are in a climb. That will give me time to get some speed while they reverse and try to run me down. Generally I have 1.5-2k seperation. I don't want any more than that. They cooperate by chasing me. Since I'm running they will firewall and WEP. If I'm getting away, I drop throttle a bit to keep them chasing. Once they are back up to 325 or so, I chop throttle, break hard (dropping flaps generally) and execute the barrel roll defense. Once again I have a brief opportunity to get my kill, or I will escape again and try over. I can slow down very rapidly in the hog compared to a spit. Couple that with the fact that the spit driver thinks he needs to chase hard, and that he thinks he's in control...
If the spit disengages, he will die most times. He may get some seperation at first, but I'll run him down. When he's forced to break again, I chop, drop, and decelerate again. Same pattern as before, but I have better position this time. If he tries to disengage he helps me out :^)
All this slow flying draws crowds. If you don't have good SA, you die. When the furball is running north to south, I make sure I escape east or west to keep the fight private...
MtnMan