I joint bodies with a jack (no.5) plane, and clamp the wood in the vice so I'm planing as normal - no shooting board.
I found a good tip for squaring the planed surface. Instead of adjusting the plane iron or tipping the plane to correct the angle, just move the plane sideways, so that it overhangs the high side of the surface - the lack of support tends to automatically correct the angle, and you're less likely to go too far the otherway.
If you're planing something wider than the plane iron, you need a very fine cut, and I like to skew the plane slightly. Remember that at first you'll not be taking much away, as the iron will only cut the high spots. It's very tempting to adjust the plane to a deeper cut, which feels like it's doing more, but is likely to cause tearout. Keep the cut fine, and each pass of the plane will remove more material. When the surface is flat, you'll take a nice curly shaving across the whole face of the wood.