Ok, we have resolved one of the problems. I used a blending medium for my sky (the one I used is Liquitex Slow-Dri Blending Medium, which I bought as part of a set of 6 different acrylics mediums, which I really like. It's a very good set to try out the various types of mediums available. I haven't tried them all yet. It's called Intro Six, and it includes clear gesso, slow-dri blending medium, flexible modeling paste, gloss super heavy gel, pouring medium and high gloss varnish).
I did a first layer with a delicate lavender, then I added a layer with plenty of white, then with Process Cyan, and then more white again. I mix the medium and the paint in a little plastic jar (it's an empty Lush Dream Cream jar - perfect for mixing acrylic medium, as it has a good lid, and the paint doesn't go dry). I did not let each layer dry out before applying the next, but I didn't apply it all in one go, as I wasn't sure what I was doing. I worked on an incline, so that the paint would go down the page smoothly, and then I turned the page around to send the paint back up towards the top of the sky. Pure stroke of luck, the paint and medium was just at the right consistency to create a subtle marbling effect, which looks like clouds hit by a very low sun, with a blue sky under them.
Still need to figure out the snow. The white paint I have on right now looks far too rough.
Note that the acrylic paper has buckled quite a bit. I should really do this on acrylic board, but that's too expensive. When I have more experience with acrylics maybe!