Ack-ack i often find myself in a high-speed stall in the 38L when I don't expect it. Dive flaps mess with handling at lower airspeed?
Use keyboard key Q to deploy flaps, W to retract flaps. Hit Q fives times for full flaps (never in combat), Q twice for maneuver flaps, the W twice to bring them back up.
For dive flaps use Shift-C. Shift-C again to retract. Dive flaps are only effective when in a high speed dive. Deploy dive flaps before entering the dive. Retract dive flaps as soon as you pull out of the dive. In real life, the dive flap switch was on the left side of the yoke. You can see this switch move in the game.
Go into the Offline Practice arena and spend some time stress testing your flaps to see how they affect your flight.