I usually use the oval diamond hone from Felco. on my pruners. (Felco 903).
It’s a steel oval coated with diamond particles similar to the EZE-Lap jones, but the shape is better suited to a curved lopper blade.
I have no clue what the grit size is.
For finer polishing I would just buy a translucent Arkansas hone and take the pruners apart, but that usually isn’t necessary.
For heavier nicks I definitely take the pruners apart, and then use larger diamond bench stones, but I have larger diamond bench stones, but those can be pricey.
Felco also makes varieties with carbide joning edges, and I might recommend those, since Felco’s business is industrial quality loppers used for agricultural use like vineyards, where workers may need to quickly hone and edge before quickly continuing pruning.