Bill,

Here's my take on touch-up paint. It's difficult (very difficult) to get a real smooth match. Part of the problem is if your paint is metallic, the touch-up paint will look 'different' because it's tough to suspend metallic in the touch-up paint.
So, in an effort to make the job as smooth as possible, here's what I do. Whenever I touch up a client's car, I use a very high quality paint brush (sold at an art supply store). The brushes that are inside the touch-up paint are as effective as doing eye surgery with a chainsaw. They tend to blob the paint on, and that isn't a good thing. With a small brush, you can get several thin layers into the scratch, which will help with the finished appearance.
After I layer the paint sufficiently, I do one of two things. Either buff the are down with a mildly aggressive polish, or use a product like the one at Langka . Either way, the trick is to get the touch-up paint as smooth as possible before applying the clear. I use the same small brush to apply the clear (after cleaning it).
It's a real trial and error thing, until you've done it a lot.

hth,

DavidM