I think the elevator trim buttons are "I" and "K". These are probably the default ones, but you should check your key assignments in the game just in case. Also, I think that "J" and "L" are for the rudder trim, and "N" and "M" are for the aileron trim, but again I might be wrong.
I've heard that using your rudder (as in swinging it from side to side) is very good at getting rid of speed. Be careful not to overuse this, as if you do you'll get that "Please do not move your controls so rapidly" message. However, I've only ever tried this when coming in for a landing way to fast, and I'm not sure if this will work when you're in compression, as your rudder might be compressed as well.
Hope this helps,
<S>
Yossarian