I found some short "propelling" crayons in Staples a couple of weeks ago (look in Kids section, about £3 if I remember correctly)- they seem to work slightly better than their chinagraph pencils (not a soft & smudgy), are only slightly thicker, come in lots of colours & have the advantage of not getting too messy (assuming the plastic cover doesnt break!) - I've tried them on OS laminated & they wipe off OK the day after, but they were no good on Harvey 1:25000 (from a different thread, the 1:25000 appear to be on different material to their 1:40000 mine has a slightly rough surface, I'd guess to help the print) - I cant clean the marks without destroying the print.....NB I tested on the cover section! (not tested in very cold conditions yet though, this may be the crayons downfall)
I have been using a small Sharpie Permenant marker (WH Smiths) on the laminated OS maps for some time & found the marks come off with toothpaste OK if you clean them within a day or so. - be warned though - after a week it seems to get a lot harder to wipe off! The sharpies also have good clip tops with a nice loop for attaching to whatever
Big problem with the sharpie perm is (appart from not coming off Harvey maps without destroying the print too!) - although great in the dry, they dont work in the wet....the crayons & Chinagraph seem mostly OK on wet maps so far.
...so I'm still looking for a good way to mark Harvey (1:25000) Maps without wrecking them when cleaning off, even a pencil seems a problem - ideas anyone?