I just posted a response but deleted it as I had read your post wrong! Yes, you could sandblast but I don't know how expensive that is. Also there are two different solutions for the etching. One is to paint it on the other is to spray on. You should be able to find these products at a craft store or even Lowe's/Home Depot. I would check to see how much obscuring they do. Also your glass shop may know.

Google "how to etch glass blocks" and you'll find loads of ideas. Good luck.

I just tied Armour Etch on my bathroom glass block and it didn't work at all...not at all. And I did it twice...Maybe there is a treatment on the exterior of the block to prevent shattering? Not sure. tried on a small jar to see if it might be defective and it worked just fine...privacy film is a major pain in the buttocks, too.