a green horse, and a green rider (not that you are green) can only really focus on one thing at a time. That is why in the French school of dressage they say "Hand without leg, leg without hand". And I interpret this to mean, when you ask with your leg for something, your hand should be passive, and when you ask with your hand, your leg should be still.
The thing is that you do each thing until you get some part of your desired response, and then you may change to the other for your next cue. It's a bit of back and forth, and as the horse becomes more capable of 'hearing ' and responding to one cue at a time, the time between your applying leg and then hand becomes narrower and narrower, until they are almost simultaneous, but never exactly so.
So, what this means to me is that when you have a horse that is leaning hard against an inside rein, counter bent to the outside, you apply rein
only for a bit until you get a response to that, a wee bit of softening, THEN you apply leg
to ask the horse to step up and into that softness.
So, say, for example, you are circling to the left, counter clockwise. Pony has his nose tipped to the right, and is leaning (motorcycling) toward the center of the circle, 'falling into the circle'.
You are 'legging' him to try and get him to bring his shoulders upright and put a correct bend in his body. You are also putting pressure on the inside rein to ask him to not stick his nose outward. you feel him hard on your inside leg, and leaning on the inside rein. You feel him HARD in his mind and body.
I would suggest abandoning the leg, and getting him to release his outward thought and his lean on the rein, and it might involve coming all the way to a halt, until he finallly lets go of brace on that left rein. When he did, I'd give instantly and let him rest for a sec, then ask for forward, and without even going on a circle, pick up the inside rein,or just flex it lightly with your fingers, and see if he'll flex, give to the rein and let you create softness there. If he does, THEN you put on the inside leg, softly, and 'flutter' it, as @farmpony84
described and you may feel him respond to your leg, AFTER he has responded to the rein.
one, two, one , two . . . ask for softness and flex to the inside, soft leg says 'step over a wee bit', then allow horse to go forward with you in nuetral. Again, again and after a bit, make each half of this equation be closer and closer together, but if things get bad, go back to "soften to the inside' .. . . . reward with big nuetral, but DO NOT reward or quit the rein 'ask', until you do get something.
People always talk about timing as being important with horses, and it is; you must reward very quickly for a good try. But, to often people don't 'stay in there' with their ask long enough to get a response that they can reward. They give in before the hrose does. And thus train in that bad behavior.