Just leaving it in the hot car/trunk for a while before first use will help a LOT, giving it more stretch/flex. Put it on while still warm of course, and you'll have to work with it a bit the first time to get it on right. Subsequent installations will be much easier/quicker. I doubt there's anything you could apply to it to make the first installation easier, temperature and patience being the real keys.
Richard
'93 Blk/Blk