Since you have already seemed to rule out pain, you simply need to work on desensitizing him to accepting you bringing those legs foward; unfortunately, this is necessary for proper farrier work, so it is up to you to get him used to the process.
Lungeing will be a huge benefit in teaching him to stand quietly, as will yielding the hips, shoulders, and backing; if he does not do any of these on line softly without resistance, work on those exercises first.
Now, work on his feet on the level he is comfortable. Picking them up, cleaning them, etc; After you have cleaned all his feet, and brushed them out good, now work on him 'giving' you each foot, backward and forward. Don't overstretch, start out just a tiny bit; if you can do that action without resistance praise and move on to the next foot. When you DO meet resistence and flight behavior, immediately release your hold, and send him out on the lunge line for some work.
The idea is to teach him that standing still is desirable, while fidgiting = hardwork. The 'harder' you work him, the quicker he can catch on, and your reaction to his actions have to be immediate for this to work, so no tying...have your line draped over your arm, so you don't have to untie, or try to grab the lead (if he's ground tied).
After you have worked him for a few minutes come back to where you were, and try again...if you meet resistance send him away; he doesn't get to relax when he is being naughty. When you only release the foot, and try to comfort the horse, he learns that this is the proper reaction to having his leg pulled forward, so NEVER simply let go and try to comfort him; you are only reinforcing the behavior; and obviously you cannot out muscle him, so use his 'flight' instinct to your advantage...a moving horse becomes a thinking horse quite quickly, so you will get more accomplished by getting his feet to move, rather than continually trying to force him to stand still...let HIM figure it out that standing still is easier than the other option (having to work).
I have used this sort of method on any horse with foot problems, be he fearful, nasty, or untrained, and it works, doesn't matter what sort of horse it is.
