1. Bin the Megs. Seriously.
2. I like the Lake Country ones. Get one of each colour.
3. Do it when it needs it, but yes I'd clay before a machining. I wouldn't on a normal wash.
4. Clay does that for you. But if you have tar stuck to the car, then a tar remover works.
5. Nope. I just use a decent one.
6. Occasionally, but using a decent product in the first place is the best bet.
Short but sweet.