Toby, I've had some experience propping branches of bur oaks in WI and live oaks in FL and NC etc., so here goes.
Props best installed in pairs, to allow for lateral movement. Props should be attached to each other to form a "cradle" for the branch, and not attached to the branch itself. Cradle should be smooth and can be lined with old car tire to avoid abrasion.
A pulley can be used high in the tree for a rope to go through and tied near the end of the branch to be propped. Pull on the other end (I've had touse a truck before)_to raise the branch so the prop can be slid under.
Depending on the firmness of the ground, the props can be held in place with bracing hardware.
On one tree near the sound I sunk the prop in a concrete footing so it wouldn't be swept away in a hurricane. No big storms since; should be interesting to see if it holds up.
Should go without saying that as in any cabling operation the lead should be pruned to lighten the load, being mindful of the "damping" effect of interior foliage. As in cabling, I look to put the support 2/3 of the way out, though this varies case-by-case.
Winter's a good time since it'll be at its lightest.
I've used treated lumber and durable wood like cedar, cypress and locust. Like cabling, it'll need regular checking.
Good Luck!