I sure don't like the idea of housewraps or anything close to the spar. The housewrap weeps moisture through and holds it tight to the wood.
I'll try to find a photo but I have a pretty simple system for my 50' main mast that's been tested for over 10 years. It won't work on the rack you're using, but if you move the spars to a better spot, it's not a big deal.
I use 3 saw horses, one close to the weight center, the others out about 18' to 20' or so. We move the stick ourselves (see pic) on a 2 wheel dolly. Once on the horses, layed on it's side, padded, I build a simple frame. 3 16' 2x4"s along each side, out 6" or so frame the spar, on edge. Use construction screws(they're reusable and the best thing building invented in years) to attach to horses and the butts which do not have to land on the horses.
Lay 3 more 16' 2x4's(of course you don't need nearly as much length) on top of the spar. About every 12' of so, run a strap of anything, old rope, fiber packing strapping, whatever, from your side 2xs, over the center laying on top, and catch the other one. This is merely to hold the rickety thing together for now.
Pad any joints on the "ridge" you've now put on top. For spreader brackets or winches, you may skip some ridge sections, or go over the top. It's not too demanding of accuracy.
With frame complete, take a new roll of 15 pound cheap roofing felt, and roll it along the ridge. Let it roll off the end.
Now, with 1x3" strapping, run a batten down each out 2x and sandwich the felt between the strap and it. Screw every 4' or so. On the ends, do a Christmas :) package wrap, and srew a srap over. The strapping/2x4's and the felt lock it all together. Now you could stand on it.
No felt touches the spar, it's wide open of the bottom, snow can pile up, gravity will keep most off.
I'll guess it takes me about 2 hours to do this for the 50'. My mizzen goes in the garage.
I save the wood but unfortuntely the felt has to be disposed of. I don't like that but until I find an alternative...It's cheap, you could get 2 lengths out of a roll.
The wood stays dry and breathes all winter as it would in a proper spar shed.
It's a big thing, this spar, but it's part of the family and well loved.