I only use it when I want a really flat hone of great size, like for doing plane irons or wide chisels. Stick it to some 12mm float glass. I don't have the 2500 grip...but I still have a little of the long discontinued 220 (may have been 240) grit! Fantastic for flattening soles.
Have you seen this stuff?
https://www.axminster.co.uk/axminster-diamond-sheet-ax974873
Not cheap, but maybe longer lasting than the Hermes.
Sorry, rather going off topic.
SAK blades are not all that hard to refinish since they are not particularly hard. Starting with polish, if that doesn't start to show results quickly, go to 1200 or 800g wet and dry. No point in persisting with too fine an abrasive. If a scratch is deep you are going to need to remove that depth of metal to get rid of it, might as well not waste time. From 1200g it should be possible to polish with Autosol.
I think a lot of people have trouble with sharpening and such because they use too fine an abrasive to start with, take too long and start to get discouraged, lose focus etc.
If you have to change grits, remember to change direction so you are taking the peaks off the finishing scratches, not deepening them.
I would advise holding the knife and moving it relative to the abrasive, rather than the usual method of clamping the knife and using a sanding stick, it is hard to clamp a SAK securely and if you get careless it is easy to overshoot a small blade and run it into your hand.