I've finally made some progress !
I've painted a couple other test models, trying to find other color schemes but this was going nowhere, so I decided to stick with the first variants and start painting the army itself. I thought I would start with vehicles to make some progress quickly (IMHO, painting squads gets boring rather quickly, and a half-painted squad isn't good for the motivation) so I took a Venom and improvised this in a couple hours:
This is the first time I'm doing any serious freehand on a model. And my first time painting a vehicle as well, actually ! It's not 100% finished (red on black requires so many layers to appear "clean"...), but it's already good enough for tabletop, I think.
Oh, and as you can see, there is a small conversion: The guns were re-positioned under the wings.All my venoms are converted this way. I'm always taking the extra splinter cannon (who isn't ?), and the placement of the guns in the original configuration seemed weird to me. Plus, I didn't like the gunner :)
I haven't bothered hiding magnets for the passengers like I did on the Raiders, and I don't think I will: too much work for small gain.