Seems like this gets asked a lot, but I'm not sure if we've been through this on the X yet, so for he record:
Make sure all your surfaces are good and clean, and then you'll need to rough up that fiberglass with course sandpaper (like, 60 grit). Do a good job at this - make sure you rough the entire surface, but BE CAREFULL! One slip with that 60 grit and you'll put a nice scratch in your shiny paint. I always put some masking tape around the edge of where I'm going to glue to catch slip ups like that.
OK, fixing the turf down. First I really don't recommend pre-cut mat sets, unless you're in a hurry. Sure they're faster, but they never look as good once you're done. If you're in a hurry by the way, then stop now. Turfing done slow looks great and is very rewarding.
OK, spend your time getting pieces cut right. Use a sharp blade - you'll need a ton of them: hydroturf blunts a blade really quickly, and there's nothing worse than a blunt blade.
Use DAP Weldwood contact cement - nothing else. Paint a coat on the ski and one on the turf. Then let it dry (feels tacky to touch but doesn't "smudge") and then put another coat on each. Two is enough for the fiberglass, but you may need three on the turf which tends to suck it right in. You know the turf is good when it has a shiny finish like varnish when it's tacked over. Put it on in thin layers (not half a tin at a time like Wasteland!!) using a brush. Get plenty of brushes too - the cheap kind from Home Depot or somewhere.
OK, You're all cut to size and ready to glue, but there's one more step for curved surfaces: hot turf bends better. If you're doing it in the dead of winter a heat gun or hairdryer works great. Now put the turf down where you need it, but be careful - once that contact adhesive bites it isn't coming back up, so get aligned before you make contact!! Take your time - you'll be glad you did.
Once it's stuck on well, push it down all over, and then bring out the rubber mallet. Yes, that's what I said - smack the living crap out of it all over with a rubber mallet and it'll still be stuck to your ski after a nuclear holocaust.
When you're trimming the edges then start afresh with a new blade - did I tell you you'd need a bunch? Any little pieces that didn't quite take can be stuck down with superglue.
If you have the type of footholds that require a seem to get the turf over, then take a look at the attached pics for my method of a very durable, almost invisible seem. You can use this technique over the gunwhales too.
Have fun!
Edit: Nearly forgot: wherever you have to make seems, use sandpaper to smooth them over. Hydroturf sands really well using a medium grit sandpaper (and then fine if you're really anal like me!)