Hi Gang,
like to hear your opinions about masking fluids. Best will be a products that available in Europe.

The only one I have tried is Humbrol Maskol, which does the job, but is a pain to remove as it gets everywhere. Will follow this thread with interest.

I like Microscale, I’m pretty sure it’s available in GB, not sure about the Continent. However, it pays to keep it mixed up though, since the metal flakes embedded in it (to show where it’s been painted) like to settle to the bottom of the container. If you don’t mix it, it dries clear, which makes it a pain to figure out where you’re applying it and hard to find a corner to peel it off.
VR, Russ

can it be used on all paints ? I think I read somewhere you can only use it on enamel

hmmm...I've used Microscale liquid mask over some acrylics, bu not all. It seems to work fine on Vallejo, Tamiya (which is actually an acrylic lacquer), and Gunze Aqueous. And it works fine on Lacquers and enamels. You might have to experiment. I have not heard that. I know some other liquid masks use ammonia or ammonia compounds as a carrier (this is what attacks acrylic finishes), but I don't think Microscale does, at least it doesn't smell like it.
VR, Russ

One thing I've used on small areas like over bolt heads and stuff is plain, old PVA (white) glue. Here in the US it's sold most under the name Elmer's glue. I use it if I'm using terra cotta paint to simulate a non-slip surface. It works well and can be easily removed with a toothpick.