Originally Posted by Richard B
Alternatively you could try a toxic thinner called Toluene.... but let's not go there!
You speak for yourself!
Ollyit, If you use gelcoat, you'll need to put wax into it or it will remain tacky and it will soon be horrible. However, after gelcoating with the wax added, it will be more than slightly slippery - dangerously slippery. Especially when wet. You will have to do more than this.
If having a good grippy deck is desirable, and it usually is, apply one coat of gel with a roller. While it is still wet sprinkle some grit onto it and allow it to go off. After this, apply one more coat of gel using the roller and containing the wax. Grit can easily and cheaply be got from a pet shop. Make a shaker from a tin with holes pierced into the bottom. Cover the top just incase you spill or drop it accidentally.
I'm presuming you realise you'll have to prepare the old deck first.
The wax is added as a very small quantity and it is often known as 'solution MW'. Do a search on gelcoat because it has been discussed often on ribnet.