Start soaking the hoof in warm water, preferably with epsom salts, if you can. That will help it blow sooner. It will also encourage the abscess to blow out the sole, rather than the coronary band (which can cause all sorts of hoof problems down the road as you try to grow that hole out). I also am a firm believer in having the horse move around as much as is comfortable, because the increased blood flow from activity will also help speed the process along. Your farrier can likely use a hoof tester to pinpoint the location and may be able to pare it out. I would (almost) always prefer that the abscess burst on its own, though, as I think it generally does less trauma to the hoof than paring it out does.
I recently heard someone mention that they had used one of those disposable hand warmers, wrapped in the hoof as a sole pack of sorts, to help draw out a stubborn abscess. I have never tried it, but it strikes me as quite clever (so long as the sole is concave enough to allow the pack enough space to not burst, since I can only imagine the sorts of nasty chemicals that must be inside).