I had absolutely no idea how to go on with the base. The answer came from one of my favourite blogs, Canadian Nail Fanatic. I added one coat of NfuOh 49 and some Wild and Crazy Twinkle Beat, quite religiously following the footprints of Mrsrexy, apart from the matifying in between.
After a layer of BeYu Mat Topcoat (Mat?!? Why Mat and not matte?? Arg, now I'm mat!) I felt it still needed something and didn't have the patience to wait for the next time, so I added some black hearts (from NDED.com) and matified them too.
I liked the nails a lot until the matifying. The BeYu did matify the nails, but it left behind a dusty white shade, a faded version of everything that was on the nails before. Shiny topcoat didn't erase this effect. Mrsrexy is using Essie Matte About You, and that's what goes to the top of my shopping list.