Touch start is nice and a better alternative than scratching.
1. The flat on the end of the tip prep is a very good idea for touch start, this is especially true with the 1/16 dia. electrodes. You risk contaminating the weld zone with little bits of sharpened tungsten when you use a very pointed tip, but even with larger dia. electrodes the flat end prep is the way to go with scratch or touch and won't have a very noticable effect on your welding performance once the arc is struck unless your working on material less than 0.060"
2. I've had better luck touch starting with a little change in my regular technique. Start by laying the edge of your ceramic cup on the work and slowly lower your electrode down until it touches. Then lever it up nice and easy with the edge of your cup as the fulcrum. This will allow you to control the distance your tungsten comes away from the work. You want it to only come up about the dia. of the electrode itself when you lift it.
Thorium, Cerium, Lanthanum, all "should" perform about the same in the circumstances you describe. However, I have found great differences in quality and ductility of lanthanum electrodes from various vendors, but that may be a little more than your asking for today.
Let us know how it works out.