im with white mountains on this one in terms of the declawing itself...*shudder*
in terms of getting him to prefer his scratching posts...try steeping catnip in water, put it in a squit bottle and spray a fine mist on his scratching posts regularly...belive me, he'll start paying alot more attention to them LOL.
also if the posts arnt tall enough most cats wont use them, you ideally want something at least twice his height when he stretches up, or something flat on the ground, it sounds though that he likes to mark vertically (clawing is also a way of marking territory) so if you dont alreayd try getting him a TALL scratching/climbing post.
when i got tempi she had a little scratching post but by the time she hit 12 weeks she lost interest no matter what i did, so i picked up one of those tall floor to ceiling ones with 3 little platforms (got it form
walmart for under $40) and it was an imediate difference, it became her absolute favorite thing, she claws it, climbs it sleeps on the higest platform, she actually uses this one even if i dont spritz it with catnip.