Was there a few weeks ago on my Osprey. I sanded - no reason not to, if nothing else it's good insurance. It's quick and easy, all you need is to scuff up the first inch or two of the hull. It also gives a good chance to fair down the keel tape and hull glass overlaps at the very point of the bow and stern.

Re: The mess, I used the masking tape that is used to trim the green hull glass to hold a 'skirt' of plastic. Glad I had it, as I used a squeegie exclusively and so made a fair mess. I'd say my garage floor is permanently a half pound heavier, though it's now fairly waterproof. As I was trimming the glass, I thought 'crap - I have fill coats to do, and I just cut off my drip skirt!' Turns out no worries - it's absense allowed me to fill the cut edge, which made the eventual fairing of that joint much easier. I'm much cleaner with fill coats, so I was only bothered by a few drips down the hull. Most I caught right away with paper towels, the rest (except one) scraped up easily the next morning. That last one I didn't notice for a week or so when I needed to flip the boat for hull sanding. I had managed to epoxy the boat to the saddles. Fortunately they were made of plastic and so released fairly easily. Bugger of a blob to sand, though.