To a certain point it is just grinding the hours out and trying not to drop the ball on too many people at once.
To help bring balance to the situation though I have reverted back to setting a standard weekly schedule. Basically, set a schedule saying Tuesday and Friday you are doing Sales, demo's and client followup. And then the rest of the week you work on product. Or reverse it if the needs are reversed. But you get the idea. Of course, when you do that it doesn't mean you ignore calls/emails. Instead you immediately respond and schedule time on the next day/time available and in that followup make sure you aren't missing an immediate issue or hot prospect. Use your calendar of choice and just schedule yourself in detail.
Like I said, I am doing this (again) and it is helping me refocus a lot, but in fairness I sometimes struggle still putting off a demo until another day so I catch myself sometimes doing a "quick" demo or talking to prospects when I should be finishing something. Every time I do a non-critical (e.g. service is not down) activity out of turn, I wind up kicking myself later because rarely is the case where it has led to a sale or where it was something that could not wait 1-2 days while I finished what I was in the middle of.
As for sales, I think if you haven't already you really need to identify how people find you and how you get them to signup. If this process is primarily human, that is a key if not primary place to focus a lot of your efforts. Signup and on-boarding need to be automatic as does the ability for a person that hits the marketing site to understand the products value proposition. Small quick video(s) and image walk-thru's help from what I have seen. It doesn't mean you stop being human and talking to everyone on the planet that will listen, just that you need the research and on-boarding process as smooth as possible so that you don't get overloaded doing work a computer should.