-I don't have the technical specifications you need, but I do know that sand blasting is being used in the outdoor advertising industry, to produce wooden signs with lettering and other design features that are raised over the background.

You may get similar, but less dramatic, results with a power washer, that you can rent by the day. It will flush out the earlywood (particularly if UV damaged) and leave most of the latewood.

I haven't actually done it, but a shop I used to work in
did outdoor signs using a sandblaster. Amazing work.
A special material with adhesive backing was applied to
the places that were not to be sandblasted. The material
would withstand the sandblasting process. You could make
letters and numbers or even pictures.
You need a sandblaster that puts out a lot of volume.
This requires a good size air compressor to run it.
And you will go thru a massive amount of sand or other blast media.
The amount of sand depends on how deep you want to etch the wood.
I can only describe what I saw being done in the shop.
I liked the effect it created, but I wouldn't want to do that work.

Pooh Bear

I would visit a sandblast shop and ask some questions. There are many other materials to use in blasting, such as glass beads, crushed nut shells, etc. Each has a different effect. Your would probably be better off finding a shop that you could take your material to and figure out the effect you want, than have a well-equipped pro do the work.
As noted above, you will need a really BIG air compressor to work with any speed at all. If you do, be sure to get a top-quality dust mask- this raises a lot of very fine dust which is not easily contained.

Interesting idea... Great minds must think alike!

I had the same idea a few weeks ago, except I planned to use it to make a new pine chest look old.

I bought a pressurized blaster pot from Harbor Frt. I got some playsand from Home Depot and tested last weekend... the results were inconclusive. My problem was that I used playsand and too many of the grains were too large to fit through the nozzle. I plan to get a screen and try again.
One word of warning, sandblasting with silica sand can get you killed. If you do this, be aware of the risks and minimize your exposure to silica dust.
Better yet, buy a large blast cabinet with a 5 micron filter and use walnut shells for media.

I'll try to remember to post a followup once I get the right size grains to test with.