Share the tool on HN, Reddit, Product Hunt, etc.
Charge $x per month.
But it is a good question and commenters should give their experiences or opinions anyway.
I would say I really prefer very "high-touch" sales, I think it's worth it, it's your first customer and you both are at a point where you can make more out of a working relationship by building the relationship itself in a unique way even if you are selling a standard product. So the more you put into it can pay off better, even if you won't be able to give as much attention to following customers or clients.