Russ,
Woody's Wheels in CO does this as well. It not really all that hard. He does do it a little differently tho.
I'd have probably used PS 890 B1/2 or B2 instead of PR1422, but that's personal preference. Also, you can buy the stuff in tubes that already has the correct ratio of sealant to hardener. All you have to do is mix them together and squeeze out of the tube. Otherwise, if you use the tubs like that, you have to use a small scale to get the ratio right.
There are a couple of different ways I've seen it done. 1st is like Ian did. 2nd is if you seal the entire flat area from bead seat to bead seat. The latter is probably more difficult, but would probably yeild a slightly better result, I do mean slightly. One idea I had thougt of was to reuse the rim rubber, and just seal it on the edges. Would save cleanup of the spokes areas, and the rubber is usually pretty thick. Downside, don't know how many years they are good for tho. The sealant is probably good for 20+years.
If you decide to do it, rough up the area you're sealing with scotch bright or sandpaper. Gives the sealant better adhesion. Next clean the area well with alcohol or MEK/MPK. Seal the spoke ends and smooth just enough so there's not alot of excess with a tongue depresser, ensuring there are no air bubbles. Let the sealer cure. Install tubeless valve stem. Install tire, inflate, check for leaks. Redo if necessary.
I've been working with PS products for years, and can tell you that I think this product will work, and work well. The only way a spoke will puncture the sealant is if you hit something REALLY hard and break a spoke off. Same thing happens if you still had a tube. The sealant isn't going to "fly" off due to rotational forces if you've prepped the area correctly. Even then, this stuff is SO strong, I don't know if it would come off, might have a small leak tho.
One thing to consider. If you have to replace spokes, this stuff is going to have to be cleaned off and reapplied. No biggie tho. Good luck Russ, and Ian, NICE JOB!!!
Mike