I have a Tandem Oasis, and have never capsized, even in big water (
knocks on wood, doomed for sure now). I have, however, practiced self-rescue much to the amusement of some beach-goers.
I'm a big guy with decent body strength.
If you're with another boat or partner, they are a lot easier to get into with help. Hold down one side while they get up the other. Reach across and grab their leg or life vest to give a boost.
A pair of swimfins really helps. Learned this while doing some snorkeling off the kayak. This is one thing in a number of these videos I see people leaving off: the power of kicking to lift you out of the water.
Last resort: take off the PFD
. It can get in the way of some people's ample belly. The PDF can then be used as a LADDER. Open it up, and put one strap around the drive pedals. You now have an arm hole hanging over the side of the boat to put your knee/foot in and get leverage to step up and get your belly up on the rail.
(Also always figured I could sling my paddle over the side with my bow rope to create a step, but haven't tested that theory).
Both myself and my kayaking younger daughter have practiced reboarding with the PFD slung over the side. Works like a charm.
There is no "one way" because there is no one-kind of human. To the guy who built a ladder out of PVC:
I would think using my PFD slung over the side does the same thing. I also have a bow rope which could be slung over the side with a foot loop to do the same thing.