How to train her to give to pressure?

[8-legged-pony]

Our RDA horse Pumpkin is coming on very well now, she's gradually muscling up and will happily canter down the bridlepath now (still wont' in the school - not sure if it's laziness or balance issues though). The main problem we're having with her, is that she doesn't understand pressure. If I take up much rein contact she'll stop dead and refuse to move. She'll quite happily trot if you give her the reins, but if you try and put pressure on the reins, to get her working into a contact, she'll go back into a walk, no matter how much leg aids you use! It especially effects the RDA kids, as they don't have the leg strength to get her into trot, and I've had to resort to tying their reins so they're not touching her mouth at all. I would think that it could be a bitting issue, yet out on hacks if she gets strong she'll start to lean on the bit - surely something she wouldn't do if the bit was causing her problems.

So what type of things should I be doing to help her to accept a contact on the bit? She's 10 years old yet as green as grass and rather stuck in her ways!

[wonkeywoody]

Personally, I would start with ground manners so she moves forwards, sideways and backwards from the lightest cue from you. She has probably got 'communication' issues from her work and lets face it, horses' mouths are extremely sensitive.
Much as I dont like lungeing too much, she may benefit from it because you can put on side reins (loosely) to mimic a contact and then you can still send her forward from the ground.
Leaning on the bit could be her just enjoying gettting out, but usually if they are leaning on the bit they are not working thro from behind and are using you to prop them up.