Hey- Abcesses can be a pain to treat.  Another treatmentoption,in addition too the epsom salt soaks is Ichthamol salve.  It smells awful but it acts as a drawing agent.  But it requires a dry place to house them and wrapping the foot.   Or you can get any easy boot. Cavello"s are the easiest to use and if you get the right size they will stay on.   After soaking 1. dry the foot some ( it doesn't need to be dripping.)  2. pack wth ichthamol. put some gauze pads over it. if the abcess is on the sole cover the whole sole. with salve and gauze. then wrap the foot with duct  tape. careful around the coronet band. Dont get it too tight.  keep the horse in a dry area.   or you can put an easy boots on and turn him out in a small  dry area.  If you  get  cavello boots, they have little vent holes in the sides of the shoe for water to come out of the boot, I'd cover those so sand and water don't get in the boot. (I duct taped the inside of my boots. It worked) you still need to make sure he is turned out in a dry area though.  you change the dressing twice daily all the easy boot cuts out is the duct tape.  But keeping a hoof wrapped on a horse can be challenging , that boot makes an already difficult chore a little easier.  Here is the kicker they are expensive and only come in pairs.  See if anyone has  a set you can borrow. and they will fit over shoes. Good luck with this, abcesses can be a bear to treat. 

Oh and I put betadine in my soak water, it makes  me feel better and it drys a little.  

I have used pull ups instead of gauze when  WRAPPING as they cushion the foot some, BUT you REALLY have to keep them in a dry area!!! Or they get a big soggy diaper on their foot. GROSS!