Hmmm... well, if it says so on the technical data, it should be alright. I just always had the notion that you can't (or maybe better "shouldn't") put 2k over 1k, but maybe that's something I made up myself
. However, 1k paint isn't nearly as hard as 1k paint. 1k paint "dries" when the solvent it is based on evaporates out of the paint and leaves the paint on the surface that you painted. 2k paint uses 2 different ingredients, which then react chemically and create a really hard surface. I think that is why I would never put 2k paint on top of 1k paint: 1k paint is way softer and weaker than 2k and therefore to me it doesn't make sense to put 2k on top of 1k. But yeah, could be that it isn't so much of a problem.
There are lots of different ways to prepare your car for a final layer. I used 2k epoxyprimer on bare metal, the parts where I welded in new pieces of metal and on the parts where I applied filler (putty) to smoothen out dents. Then I applied a layer of 2k filler and on top of that the final colourcoat. The filler I sprayed is basically a thick primer (which can't go on bare metal by the way, so the bare metal first needs to be covered, in my case by the epoxyprimer) which you can sand pretty well to smoothen the surface perfectly. That filler I really needed to stirr a lot, since there was a big residual of derry on the bottom of the paintcan, which shows that it's a thick paint with a lot of solid particles in it. Really nice to work with.
But just look around, ask around at a paintshop. When you ask a lot of people or here on a forum, you get a lot of different advice, which makes it hard for you to decide what you should do. Doesn't mean the advice isn't correct but there are just a lot of ways to do it and every situation might need a different approach. In a paintshop they'll tell you: "you should do it like this and that" and then you can just start with it. Makes it a lot easier. You can also ask them what to do with the coat of Rustol you already applied.
Last thing about the Rustol: 1k paints don't get really hard, which causes them to be very hard to sand with sandpaper (unless it's been drying for years). Your sandpaper will tend to clutter up with paint really fast, especially the 600 - 1000 grid santpaper that you'd wanna use when you're busy with the paintjob of your car. That's another reason why it's not so handy to use onder a final coat (of course you can smoothen it with filler, but it's not really very convenient).
But I'm also a hobbyist, not an expert.