I read the many health articles and guides online and was dissatisfied with the blister care advice. Blisters are common problem with athletes and active people. With 10 years of experience working with renowned physical therapy & sports injury center, I'd like to offer my instructions on blister care that will result in easy callus formation rather than unnecessary suffering with ripped open hands.
1) do not remove the top layer of blister skin unless it has torn open and is in danger of ripping away healthy skin. If it has torn, go ahead and trim away the loose skin.
2) if the blister is intact, wash hands with soap and water, then drain it with a clean needle (sterilize with rubing alcohol), making a small hole, near the edge of the blister. Use repeated pokes in the same spot and pressure on the blister to get as much fluid out as possible
3) using athletic tape, tear a 1/2" wide strip, a few inches long. Fold over the end about 1/2 inch to create a non sticky patch, then place that patch over the blister and wrap the tape around the finger. Bend finger slightly (into good gripping position) to ensure the tape is not too tight to allow holding the oar, but snug enough to gently hold the blister "closed" and limit the refilling of fluid. You will probably have to drain it more than once, but if you do this the skin will often seal back down and form a nice callus instead.
4) if you notice a hot spot (Pre-blister irritation) tape it to protect against blistering, let the soreness subside, then go un-taped again. You want to irritate the skin enough to callus, but avoid full on blisters if possible.
Hope this helps save some hands!