Well, I did told:) I'm trying to control 2 steppers with RC controls, in servo style (this is what I mean by proportional).
So I have PWM input. Read it from appropriate channel, map it to desired range, i.e. impulse length 1500-2000 map to 0-400 range (400 steps for my 1.8deg motors with halfstep setting should make full rotation). And trying to use moveTo() func from Accelstepper lib.