... going to try “hydro blasting”!
You will love it. I had my entire Kawasaki engine [heads, cylinders and case] vapor blasted a few years ago before a total rebuild.
Steve.... a friend had a few castings done locally and they really look fantastic. The block and head are so hard to prep that I’m excited by any option. Did you paint or leave unfinished?
The Kawasaki Triple engines came "naked" from the factory, so I didnt paint, still looks great 3+ years later.
But you'll need to paint the Sandie, not sure what further prep will be needed but have read it is great even if it will be painted.
Plan is to paint!
I had my K0 engine cases vapor blasted, which was way more expensive than just bead blasting, but I was so happy with the finish I didn't bother to paint anything except the top and bottom cases. Vapor blasting is excellent for sure, but is not as aggressive as bead blasting, so to get the baked on crud off my cases, the blaster first chemically washed everything, then bead blasted it, and then finally vapor blasted it to close the pores in the metal and give it the "sheen" that I wanted.
I don't think you'll be able to successfully blast the bottom end without a complete engine strip John, but reassembling the bottom end is easy peasy, so if it was me, I'd strip it down to completely empty the engine cases, and the benefit is that you'll be able to check all your gearbox bearings, primary chains and tensioner, install a new cam chain, and maybe new main bearings while you're at it.