Absolutely, make sure you clean the part really well and plastic primer will let your paint stick better and will make the paint job look nicer for longer.
I've had good results with spray dye, e.g. VHT vinyl spray dye. It soaks into the porous WSF, so it won't chip off.
Thanks for that, I didn't know about this! I've added it to my personal list I maintain specifically for building stuff.
Just make sure to use a water-based sealant/paint and not oil-based (they'll pit). Minwax Polycrylic works great for WSF parts, I've found.
Tamiya Fine Surface Primer works well with WSF (and FUD), once a couple of coats have been applied the surface is good for Acrylics or enamels. Spray Acrylic (Humbrol brand) works well straight onto WSF too. but generally needs 4 or 5 coats.. Paul