One thing you can do to FORCE water into a tight, circling root-ball is to lower the entire pot into a bucket of water a few inches lower than the rim of your pot. Or use a filled sink. After a few minutes, the root ball is 100% soaked with water.
But you have to hope that enough water drains back out fast enough, or the plant can drink it up fast enough, that your remaining root hairs don't drown.
