Ross -
Gelcoat: use ultrafine rubbing compound to get out the scratches. Mequiars has a good one at autoparts stores. Mast: ask local sailmaker who will have setting as lbs tension for uppers and lowers. In general, adjust uppers with lowers having no tension, tighten/loosen each side till mast is in center of boat (use main halyard to measure to same spot, say the chain plates, on both sides). Once in the center, tighten each side equally, say 3 turns of the turnbuckle (can deflect ca. 1-2 inches when you pull on the shroud when standing up); now tighten lowers to about the same point, but sight up main track to make sure its straight..adjust port or starboard lower to make straight. Go sailing in 12 - 15 kts breeze with full main and working jib on a close reach or beat. Is the leeward upper loose? If so, tighten until it isn't, but not much more; now tack and adjust the other side. Now sight up the mast and see if the middle of the mast is sagging or bowing to windward; adjust this with the lowers so the mast is perfectly straight in this breeze on both tacks (hint: always adjust the leeward side). Buy a Loos tension gauge and record the readings, sail around noting speed, pointing, etc.; adjust rigging (tighten or loosen), read tension, sail around...better or worse, etc. It's an empirical process actually, but the gauge will allow you to reproduce your settings when you take the stick down, etc.
Sorry I don't have the #'s for a 24 though.
Cheers, Greg

I'd hire a rigger to help you out on your first foray: Take copious notes, ask lots of questions, and then try it on your own.

If you're determined to try it on your own, here are some suggestions:
1) Good tensioning gauges cost lots and lots of money ($1,000-plus); cheap ones aren't worth the bother (and may not work on rod rigging).
2) Rig up a measuring device as follows:
* Get as large a sail slug as will work in your mast track
* Attach a ring and dog clip (the kind that clips a leash to a dog collar) to the sail slug
* Get a 50-foot measuring tape
* Insert the slug in the mast track, attach the main halyard to the ring, and attach the dog clip to the tape.
3) Run the slug with the tape attached up the the point where the lower shrouds attach to the mast.
4) Measure to the base of the shrouds and adjust the lowers until there is modest tension and the measurements are equal.
5) Put your face against the mast and sight up the mast track to see if the mast is straight from the deck to the point where the lowers attach; if it is curved athwartships, the shrouds are too tight.
6) Repeat the process with the uppers.
7) Continue adjusting on the water; if the leeward shrouds are loose when hard on the wind, tighten things up: Start with the lowers and add full or half turns (depending on how loose things are) to each turnbuckle, then repeat with the uppers. When back at the dock, sight up the mast to check for athwartships curvature.
Mike Fordyce
K. 361 (C&C 40)
Point Richmond, Calif.