Why not just melt the block and add as a liquid? Seems like shaving it is a lot of work. I have used melted wax several times with no issues. I'm using a cement mixer, probably wouldn't work with the solar method.
I ended up making several batches of waxed sand this season and tried wax from the trap supply dealers, Hobby Lobby beaded wax and their block wax. My quiesenart bit the bullet flaking the block wax so I got a thrift store double boiler and melted it and then added it to the warm sand in the cement mixer. The flake wax or beaded wax works the best for me in the cement mixer. I run the sand temp up to around 150-160 and shut the heat off. It's clean play sand with no organics. After the wax is added, I run the mixer until the sand gets back down to 70° and have to keep an eye on it so it doesn't build up on the sides of the mixer. If it does I wipe it off with a gloved hand and let it continue to mix. The melted wax seemed to be considerably more prone to this than the flake or beaded wax. The Hobby Lobby beaded wax seems to be the best option for me, cost and convenience wise. It comes in a three pound bag which is perfect for my mixture. I use three pounds of wax to two 50 pound bags of play sand. That held up to some pretty cold weather. The only time I had traps inoperable was when we had snow, thaw, rain, freeze and ended up with a thick ice crust over the set. The sand was still loose but the frozen snow was the culprit. Once it was removed, the sets continued to work.
I'll be making a lot of it before next season. I should have started with it from day one. I missed a fair number of coyotes early due to frozen traps.