I have the crowning tool you showed, it's a good investment. I did a level and crown on my agile al3000 lp copy but I leveled the frets with a diamond dusted steel plate that was made for sharpening knives.

I used it to rock on the frets and hit the high spots found. Then using the markers I crowned the frets with the tool I bought.

The fretwork on this guitar was quite decent to begin with but after this job it was better. I was able to lower the action a little more.