The adhesive backed sand paper I use is from a brand called sunmight, its the cheapest adhesive back sandpaper I can get and it works great. I think it only comes in 3in wide tho. I cut it with a razor length wise for the smaller sanding blocks I use. What paper did you use before? 1 leveling block with 180 would normally last me at least 5 fret levels back when I was doing production work.
The z file is the way to go but if you dont want to spend the cash I'd get those crowning files that phili luthier sells. I personally don't like the diamond files, they do the work way faster but getting the scratches out of the frets takes longer vs. a normal metal toothed file. I have done that block at 45 trick but only on guitars that needed fret work that the customer couldn't afford. I wouldn't recommend doing that, you'll get weird intonation spots on the since the frets aren't fully formed back to the correct shape.
Do you adjust the nut slots when you set up your guitars? having the proper height at the nut makes a world of difference in the overall setup and it can help get rid of fret buzz sometimes.
I'd give you a skype lesson on how to set up a guitar if you want. Shoot me an email if you want to set that up.
info@hyperionguitarworks.com