Molotow One4All 227HS 10 Set - Basic Set 1 - 4mm Paint Marker Pens

can these be used to paint signs on old barn wood, which would be left outside year round?

How much paint is in each pen? Would it be more cost-effective to buy fluid acrylic paint and use applicator bottles with needles to draw?

Do these really cost $58 bucks? for paint markers? and do these meet nyc subway graffiti standards of the 70's?

It says that the tips are exchangeable. Does that mean that I can put a 4 mm tip into a 2mm marker and a 2mm tip into a 4 mm marker?