Hi,

They look like they'd be fine with most casual foot wear with
any sort of decent grip sole. For slippier smarter footwear I'd
say just learn to live with it, though it seems some form of
renewable coating fore and might help, but what ?
Thing is I can't see any treatment lasting long at all,
though sand mixed with varnish seems worth trying.

rgds, sreten.

If you never used the other side you wouldn't probably
think they are slippery, most pedals are slippery if
your pedalling technique is based around using SPD.