Depends on how contested the areas I'm guarding are. I can usually get a good splat-to-splatted ratio by playing to the weapon's strength of suppression. I played mostly on Bluefin, guarding our side of the stage from invaders and slowing down their advance; the only real threat to me was usually chargers. If it was clear, I'd move down to one of the paths to advance my wall so to speak, and harass opponents on the other side as well. Here's a trick, start your charging behind cover to minimize exposure.
Oh, and the echolocator is great for maintaining a constant stream of bullets.
Yea I know about using the special to refill the ink as well as revving behind cover, I do that all the time :)
Although in my experience...the Hydra takes a lot longer to get it than most other weapons. I could literally have it half filled while focusing on inking and someone else has already triggered their echolocator -_-
Bluefin is a pretty decent map for Hydra IMO, provided you have at least one teammate capable of holding the other side as well. Some of the trickier maps for me are Moray Towers and Port Mackerel (once again it's fine if you have team mates who can hold at least one other lane...otherwise it's GG).
I point these out because, I have a lot less trouble doing these things with the L-3D...yes it's an offensive weapon but it also inks really well. In short, the Hydra is super specialized, almost to the point of detriment. Wouldn't be surprised if Nintendo buffed it's inking ability by a smidge in future (similar to what the L-3s got in 2.2.0).