Depending on the area, why not cover it with the 'waterproof' type carpet of
synthetic lawn. Years ago when Cyril Lord was making very cheap carpets, he
produced a 'carpet' called "Cyril Lawn".

Someone else has suggested sand in with the paint and another raised the
question of it being 'sandpaper'. I would look into a synthetic surface.

There is a surface made of old tyres, but I believe it to be a compound to
be mixed like concrete and laid, and rather expensive. Found under
children's play areas as supplied by councils and fitted at Motorway Service
areas

Few ideas :-))

Mike