I've been using Turtle Wax Color Magic. It comes in colors. In my case black. This year I picked up some Turtle Wax Color Detailer for black. Both products work reasonably well. My old Harley has marginal paint. This stuff hides some of the damage.
Unfortunately black is the most difficult color to remove scratches from, and keep looking good, but any dark color is almost as bad. I have a black '02 Vulcan 750, with swirls, and just gave up. The problem is the clearcoat. It is a LOT softer than the paint, and trying to polish it seems to make it worse. In my case, I am considering having it painted a lighter color, but this is just a basic bike, tank and fenders. White paint has the same swirls, you just can't see them like you can with the dark colors.
Ive used this stuff for years on black paint just get some black shoe polish and put a layer on and then buff it out do this a few times and the swirls will go away then put some good wax on top of it like Meguairs put a few layers of that on and it should look good
I almost forgot. I don't know if you can still get it, but Honda spray cleaner and polish worked well for me. Very similar to furniture polish. It leaves a coating that kind of fills in the scratches in the clearcoat and gives it a wet look. Of course it has to be reapplied quite often, and that would be quite a job on an 1800. I don't have a good answer. I have seen a lot of high dollar black cars around here (Mercedes, BMW, etc) and they look terrible, while the light colored ones still look almost new. I have a black Ninja 500, that I bought new in '09, and it also has a lot of swirls in the clearcoat, and several scratches on the tank from using a tank bag.
I know I'll get some chuckles, but the best polish I've found is Kit brand, sold at autozone in a yellow bottle. It's called Scratch Out. It's basically cheap generic brand hand polish, but I tell ya, it turns what ever finish you're workin' on into glass with little effort. I've done side by sides on panels with 3M, Turtle, and Meguiares, and every time I wind up back at the Kit brand.
Dave, I have been using zaino for years and it does give a beautiful result, from a distance. Close up, however, my dark green paintwork has developed some swirls. I have always used their flagship product, i.e. what is currently called the Z2-Pro, with a few drops of the additive currently called ZFX. Looks like I should try their Z5-Pro to remove (or fill) the swirls...have you tried that at all?