If you're using Norrells over an existing finish, such as anodizing or park, you're good to go unless the finish is old, and worn smooth.
If this is the case, you need to blast, in order to rough-up the surface of the metal. The ideal media to use is fine grit aluminum oxide.
You don't want to remove anything more than you need to.
Sand will work, but even when careful, it WILL eat into the anodizing, then it leaves a crappy looking rough surface due to its larger grit size.
The a.o. will also eat into an existing finish, but due to the finer grit size, you have more control with it.
BTW, this blasting is not an option .... and hand sanding doesn't work.
If re-working a receiver that removes a large area of the existing anodizing, I'd recommend having the piece re-anodized. Then if necessary, use the Norrells to match colors. Norrells is a fairly hard finish, but nowhere near hard enough to use in place of type III anodizing.
As far as de-greasing, I prefer to 'soak' the pieces for at least a few hours in something like acetone, then give it a final bath in MEK.
You can use brake parts cleaner (non-chlorinated), but do NOT use carb. cleaner.
One more thing .... the 'tape-test' isn't always a good indicator for a good finish. I've seen bad finishes that will still pass this test.
It has to be REALLY bad to peel off with tape.