I never sand blast a engine block, always use wire wheel+degreaser and sometime hot tank. Sand cant dissolve and even the best filter don't catch everything. Kohler K series don't have filter system that's why they require non detergent oil or today new synthetic oil.
I'm not confident enough to try your method Tim unless you use walnut/almond shell or maybe soda but sand or glass look pretty scary to me! Now what kind of coating you have in mind for this engine? I know you got a nice oven now so is it powder coating or maybe ceramic coating? For us poor home DIY solution are limited to high temp paint (Primer/color/clear) like VHT or maybe a cheap Eatwood powder coat system and solar lamp
PS: Link for Mr "Average Joe" to VHT site and a abrasive gun to try media blasting for cheap has dirt..
http://www.vhtpaint.com/high-heat/vht-engine-enamel
http://www.eastwood.com/blast-out-of...asive-gun.html