I’ve used Global knives since Anthony Worrell-Thompson was a tv chef and started off with a wheel device. After a while moved onto a ceramic “steel” but found that neither really worked too well.
So I got a combination medium/fine grade whetstone and that was much more effective. After a while I couldn’t get a proper edge on the knives and seriously thought at one point I had fake knives. But then bought a rough grade stone and after many hours graft got an edge back on the knives. Took a lot time and a lot of effort though.
Now, I realise that Global knives are just very poor at keeping an edge and have to be constantly re-sharpened. The medium grade stone works fine if used every couple of weeks, and if you get the sharpening guides, is very easy to master.
I did make the mistake of keeping the stone too wet, so it didn’t allow any residue to build up - and that’s what actually sharpens the blade.
If you do get a whetstone, buy one that comes with a non-slip silicon mat- much better that those in a plastic box, they get very messy.
One final point, if part of the attraction of Global knives is the way they look, then be careful with a stone. Because Global are one-piece it’s easy to scratch the handle join if too enthusiastic with your to-and-action.