M390 and even moreso k390 have a good bit / lots of Vanadium carbides. Diamonds and CBN are going to be your friends here.
Depending on which Nubatama you are talking about I'd put them in the 1.5 to 2 range along with the Shaptons. All good stones but you are relying on removing the steel around the Vanadium carbides until the carbides fall out. Diamonds and CBN are a much better way to go here.
So you have several options. Diamond films work great here. Yea I know they aren't popular here
Especially the heavy duty films are excellent for this task. So do CBN and diamonds on strops and belts if you are going with a powered approach. You can supplement your waterstones with CBN or diamonds in matching grits. This will make a far bigger difference than what stone you pick.
Diamond plates are essential for getting things started especially if you are reprofiling - changing bevel angles. I prefer the Atoma diamond plates as an excellent start. I don't care for the XXF DMT plates - I've had excessive diamond fallout and patina develop in excess on the nickel matrix supporting the diamonds. And the finish leaves a lot to be desired. I tried a couple of them before giving up on them. So this gets you to 1200 grit with either DMT (XF) or Atomas. From there (~ 16 microns) consider 8 micron CBN, then 4 then 2 microns. This will leave you with a very respectable edge, but of course you can go much further - 1, 0.5, 0.25 0.1 microns .... For the abrasion resistant steels, I prefer small jumps in grit sizes rather than big jumps.
I think jumping from ~ 16 microns (1200 is a bit coarser) to 1 micron (16,000) is way too big of a jump - especially on an abrasion resistant steel) and the XXF is again not something I've had much success with.
Given the right abrasives, sharpening M390 is no big deal. Given the wrong abrasives, it's a PITA as are most abrasion resistant steels. Personally I like abrasion resistant steels since steels that are abrasion resistant tend to hold the edge that you worked to achieve much longer.