Alright, so yes adjusting my last post. And have edited my initial post to make sure I'm being totally transparent with it. This is a representation of my opinions, and no-one elses. But we'll also be keeping that part out of future posts too
Waterslide decal paper was from Eckersley's. It was an interesting thing to deal with because the decal goes clear in water, then dries white again (but a different white from what it originally was). But it reacts favourably to Oil finishes (the instructions say spirit or oil based varnishes, but I suspected Tru-Oil would work as a result.
Also unlike a lot of Waterslide decals I saw online this one: 1) didn't need a clearcoat to seal the ink in, and 2) didn't need to be printed reversed. The paper waterproofed the ink on its own.
Oh but I should also note: In some of my tests, and on the final decal, it did need a couple of coats of Tru-oil before it went fully transparent.
Test decal for reference (the white circle was just the backing side of the paper, i got worried that I'd printed on the wrong side initially lol):