Got some decal solvent and tried it out.
Got a message from the local game store letting me know they’d finally gotten some in, so I swung by. Decided to try the vallejo product, and grabbed the wrong one. Discovered that after entirely too much time on the internet, where absolutely everybody seemed to have a different opinion about vallejo’s ‘decal fix’ and ‘decal medium’. In one case, an illustrated tutorial explained which was which while mixing them up. The text and the images completely reversed the process. Brilliant!
By last night I had eventually managed to get the right stuff ‘medium’ is the solvent (it says softener on it, but I’d missed noticing that the first time).
The devastator markings came out beautifully. Totally can’t tell the difference between the decal and the paint. Actually brilliant! That said, I already had those cut so perfectly that the pauldrons didn’t twist them much. The real challenge lay in my reversed space wolves markings, since they’re much more solid and were reversed to boot (not sure how big a difference that made, but they didn’t seem to stick as easily/nicely). Still. Very happy with the end results…