Learn it in a controlled environment prior to depending on it in an uncontrolled environment. I found there are a lot more nuances involved in scrambling back into a stable sit-inside sea kayak than a considerably less stable surf ski. So just practice them. Rolling and bracing are the most effective and reliable, and least energy-consuming. Re-enter and roll is next if I’ve swam out of my kayak. Scrambling back into a flooded cockpit takes the most skill, balance, and energy for me. I find a paddle float can be a big help even in rough water. So just practice all these things where there’s no big pressure for an immediate and high percentage of success.
But just for the sake of theoretical, it’s incredibly important to master the more-difficult re-entries of sit-in sea kayaks prior to putting yourself out there. I suppose something like jumping into the 12 foot end of the pool before ever trying to swim in shallow water. It’s something that’s best to accept and have fun with.
I actually picked up a battery operated pump for such solo paddling situations. It’s not a permanent fixture. I just treat it like a hand pump. It’s accessible if needed, and then I can flick the switch, put on my skirt with the hose running out the side of the skirt, and have hands free on my paddle while the water pumps out. I’ve never had to use it for a real situation. But as you point out, the situation where you capsize is probably one where you may want to keep both hands on the paddle.
Also, pumping out a flooded cockpit is no small task. I’ve learned, in scramble rescues, to go to the bow, take a deep breath to fill my lungs, and try to lift the bow as high as I can while I quickly twist it upright. It seems a fairly good way to cut down on some of the water left in the cockpit. It takes a few seconds to follow the lines to the end of the bow to lift, then back to the cockpit. It’s also a good way to train yourself to never have both hands off of the boat at the same time. Always have hold of the deck line with at least one hand as you move your way to the end of the bow and back. It’s not necessary in calm conditions, but may be crucial where you would actually need it. So I think it’s a good way to build and reinforce good habit.
The actual scramble moves themselves, with and without paddle float, I think are best done on the water. I’ve found instances where what I find easiest doesn’t work at all for someone else, even just for getting yourself up on the deck of the kayak. I started doing a cowboy scramble, and still practice that. But have all but abandoned it for what’s locally been labeled a cowgirl scramble. I think without considering balance issues and personal preference, the cowgirl has to be quicker and less work just as a matter of the total of the moves themselves.