Umm the usual thing to do I think is drop the player that put you over the cap (so do a drop on the draft site) then pick up an available FA and insert it where you dropped the other player. That player will be available to all until post-waivers - which at that point you can re-add the player (assuming you can find the room).
Need MM to declare his ballpark (ie pick the park he is going to use on the draft site)