I use both PR Spearmint and their Avacado. I have to cut either ink 50/50 with water in order to be considered useful in my journals. This formula dries very quickly and doesn't smear. I'd expect Sherwood Green to respond the same.
I draw up some ink in a syringe and then draw up some water. Using the syringe, I then fill either my converter or maybe even refill an old cartridge. No water touches the ink in the bottles.
Yes, the colors are just a tad bit lighter, but the shading is still wonderfully pronounced and the ink still flows smoothly over the paper.
Your mileage will vary of course...