The reply from music logic was very good and thorough.
I would add, that once you install frets initially with glue... the glue builds up under the fret, and you're stuck.... if it didnt fully seat, the glue under it wont let it fully seat....
Should get the frets in, THEN glue.
Steel channel is not to be trusted for fret levelling.... Find a chunk of 3/8 or 1/2" aluminum in a length you like, and take it to a machine shop to be surface ground dead flat...
As to higher frets buzzing.... This is very common, especially on tighter radiused boards like fender uses.
The solution is easy, though many people dont know of it. It's generally called "ramping" the frets. When you initially level the frets, *ALL* frets are supposed to be perfectly level with each other.
Once thats accomplished.... using your true flat sanding block (I use surface ground aluminum) You take off more from the last frets- Keeping all those frets level to each other, but angled lower to the rest of the neck....
My block is about 7? inches long. and about 2.5" wide. I use the narrow side of the block on the 24- up scrubbing more off the frets, but putting most pressure on the 24th fret. Then I use the block lengthwise, doing the same thing again. Most pressure on 24, least pressure at the lowest fret the block touches, and scrub it some more, until every fret under the block is in a flat plane, but that plane is angle lower then the rest of the neck. So... the higher the fret, the more the frets "fall away" from the string path.
It doesnt take a great deal of "ramping" to fix the high fret buzz common on tight radius boards. But it solves this common problem quickly and easily.
I think everyone should be doing this... but a lot of people dont know about it.