if you have the money... there are a number of "garden shredders" they are basically very light duty electric wood chippers. they are, as i understand it for composting small sticks and yard debris into something more compost pile friendly.
i dont remember which is it, but one of them is the perfect size for a peat bale... meaning you can just cut it open and pour the contents through the shredder. this will basically fluff and homogenize the contents of the bale into a nice consistency ready for adition to w/e.
pretty sure they are like 5 hundy? idk ive never even seen them in stores tbh.
TBH, if you are using a bale in one go... you should just get a nice good quality wheel barrow. karate chop the bale in half and just dump it all out and work it over with a shovel.a good wheel barrow is one of those things you will never regret investing in. rubbermaid makes very nice 2 wheeled models that are like 10 cubic foot. they are sold as "garden carts" i think.
on another note... if you think shredding promix is a PITA... you should try shredding cheap crappy Mexican Sedge peat bales... they are basically 10% sticks, and very very lumpy. promix uses really nice fine sphagnum that's very nicely sifted and free of debris.
if money was no option i wold probably stop making my own, and just buy BX bales and add more perlite.