Sorry for bumping...just my two cents...
I'm afraid magnetic paint is no good at all, it hardly has any strength to it whatsoever. Waste of time.
Here's what I would do.
I would use blackboard paint for the wall (you know it doesn't have to be black, you can get it in many colours now - although black can be really cool). Then I would measure the map you want to hang and get a magnetic steel sheet cut to size. Something like this: www.diy.com/nav/build/building-materials/materials/metal_sheet_material/-specificproducttype-steel_panel/Steel-Panel-Steel-Coloured-L-500mm-x-W-250mm-9284136?skuId=9293836 or this https://besttoolexpert.com/chalkboard-paint/
Failing this, I would get magnetic steel tiles from somewhere like B&Q (as above) and then trim the map to size. I would mount the steel sheet/s on to the wall and then I would very carefully stick the map on to the steel sheet/s with good quality pva glue. When fully dry and free from wrinkles, I would do several coats of PVA glue on to the surface of the map. This will make it durable.
Take a magnet with you when you go to buy the steel sheet just to be absolutely sure you're buying the right thing.
There are a lot of cool YouTube videos on this subject, here’s one of them. Good luck
