Recently, we were playing in fiberglass race kayak (oops.. no floatbags) that sank till it was vertical in the water. Turns out it is very hard to right a vertical kayak when it doesn't have any floatation. (Besides adding float bags) Any tips on rescues: one person in a boat, one person in the water, and a vertical kayak?

Take swimmer to shore, leave kayak.

In order to empty the kayak you need to get it somewhat horizontal with some freeboard so that as you pump it out/empty it out it doesn't continue to refill. This is incredibly difficult (read impossible) with a swimmer and a single other kayaker. If you're feeling particularly stubborn you can try to tow the vertical kayak to shallower water, but that isn't much easier from impossible.

Find a block of styrofoam floating around, or on shore (it's all over the place) and cram it into the verticle kayak. Pump excess water out.

I'd have to agree with Mark on this one. My future father-in-law tried out one of my kayaks back in the days before bulkheads. The boat was "so stable" we didn't bother with putting the float bags in. He somehow managed to tip it over, slipping out as it went over not even getting his head wet. My wife to be quickly rescued her dad taking him to shore while I very slowly towed the vertical kayak toward shore till it ran aground then dragging it to a more horizontal position to drain the water. In our case it couldn't have been pumped as the cockpit was not above the waterline when the boat was vertical.

Needless to say we now have bulkheads and still never leave shore without backup flotation bags inside the watertight bulkheaded compartments.

Have also seen this done with a 28' Inland E-Scow sailboat. A very slow tow to shallow water with that one. Thank goodness done with a small powerboat.