There are proprietary products you can use on wounds and pruning sites, although I don't know anything about them. I have used Stockholm tar, although it drips a bit on vertical surfaces, and thick Vaseline but I think that because of the danger of silver leaf disease you might be better with the proprietary stuff, from a garden centre.
It all looks very neat now and the area covered by the tarp looks just the thing - you have been busy
You might need a couple more pallets in the middle of the tarp if a big wind is forecast. Oh and an allotment site wouldn't be an allotment site without doors everywhere
Anyone who has found doors in a skip will carry them back to their plot as proudly as a hunter with an eland. Skip-raking is another side of allotmenting which you soon pick up
I wish I had your energy now.