Flaps are interesting, they're an art in themselves.
I rarely go into horizontal turns when fighting in my Mossy, only when I have to. If it carries on for awhile I might kick out my flaps, but I use the Mosquito's vertical strength in dogfights more. In Spitfires I'll tend to scissor and barrel roll.
My favorite tactic is to bounce someone with a few thousand feet advantage, and if someone starts closing in on my six, I'll go straight vertical, WEP, then when my IAS hits about 160 and the Merlins start trying to spin me I'll kick out two notches of flaps and full stick back, almost tail-flipping it (a trick I learned in the 262
) and allowing me to drop in on their tail after they bleed energy chasing me, while I get to use the Mossy's killer diving power and guns.
In the Mosquito's case, I don't feel bad for using a big alt advantage and BnZing at times. I still prefer a good old turn fight, but the late game monster planes make the sky really unfriendly to a 1943 Mosquito. She gets outpaced at most alts, so I have to count on starting the fight at the top. She's a quirky enough bird that I don't feel guilty for the occasional BnZ kill.