I've put together a little video on topping up grip. Now apologies for it being a bit boring but it's difficult to make this exciting! Still, I hope it's useful for those who need it.
You will need:
1) Good quality masking tape.
2) Flexible plastic spreader - DO NOT USE METAL!
3) A tube of Sikaflex FC11 Sealant (or your preferred alternative)
4) A nail brush.
6) A bin close to hand.
Any questions then feel free to get in touch.
EDIT: US readers please read this article: