Can you practice with your bike on a trainer or some other 'hands free' way of staying upright and still?

I had SPDs and had them cranked as loose as I could get them and I still crashed and was still clipped in. It's a mystery to my friends and the LBS as other people have no problems. And I have BIG FEET! Haha...
For mtn biking I don't use them at all, but on the road, well when the foot is better, I will. If you are mtn biking with them, I would try doing your getting in and out on the road or a very easy trail first.