What has been called vapor blasting is more commonly referred to here in the US as dustless blasting. It can use different medias but they are always mixed with water, thus the name dustless blasting. I don’t know what the gentleman in Texas might be doing that is unique, but vapor/dustless blasting is offered just about everywhere these days.
I think the term “vapor” is a misnomer. it does not miraculously vaporize but instead leaves a muddy sludge which I suppose has some advantages over a dust storm. 🤷♂️
I would never consider any media blasting on an assembled ZF. Strictly an approach to do on an empty case.
The beauty of Dry Ice Blasting is there is no media to get blown inside and grind up the gears. The “media” is the dry ice and yes it does turn to a vapor, with the only residue being left behind is the material that was removed from the surface. For this reason it is often used in food processing facilities on processing lines
do a YouTube search for Dry Ice Blasting and you will find there are specialists in the automotive hobby world working wonders with this approach
Larry