[GT40's]

I used similar paint to what you mentioned, Black magnetic paint base with waterbased craft paints over it ,then road markings and detailing. After painting I sealed it all with watered down white glue & the tape went on.I dont know how it compares to other methods cos its all ive tried so far but im happy with it. The magnetic paint was a waste of money though as it hardly changes anything! And I didnt paint into the slots with the magnetic paint ,just on top. The magnetic paint had 2-3 days to cure after I aplied a couple of coats.

 

[GT40's]

Just another note on aplying copper tape on PVA paint ,in hindsight and for future Ill try some sticky glue before putting down the tape as its more likely to come off or wrinkle due to wheather changes on a phorus PVA than on latex paint.

And about the magnet traction on routed wood tracks, another way is to inbed mettal wires in routed slots and cover it up.