Jedi-Mike - a Panzer IV Ausf what?
if it is a D, then the tank could be all grey.
Tamiya suggests XF-63 (German Grey), but some of us think it is too dark and use XF-53 (Neutral Grey)
Bill - I did my Panther road wheels w/ a Sharpie over Tamiya Acrylics last night w/ no trouble.
also washed one w/ artist's water color based wash and it went fine.
(i guess i am the only one who does not use oils for this!)
Chris - I agree w/ Sherm. When i did mine last night, each wheel was mounted on its own 'stick' (i use sprue).
that lets me spin them w/ one hand while i hold the marker w/ the other.
my fingers kept clean. (i still have CA on them from doing the PE!)