In the mid 1970's, since there was no internet and thus no gallery websites, in order to know what kind of work a gallery specialized in, you had to visit it in person, or depend on their print ads in art magazines. When I had researched, visited, and zeroed in on five or six galleries in a particular area I thought might be interested in my work, the next thing I had to do was prepare a package to send them, via snail mail. This would typically include a sheet of twenty slides, again my BEST work, a separate typed list of the slides with title, size unframed, size framed, medium and my price (not necessarily the retail price), my bio sheet and my artist statement. The cover letter said that I had visited the gallery, believed my work would be a good fit, and requested an appointment with the owner or gallery manager (and I made an effort to find out the name of this person) so that I could show them a sample of my work in person. Then I waited for a phone call or letter, or sometimes just the return of my package with no comment at all. If I had no response or return of my materials after two weeks, I called to simply ask if the package had been received, and ask when might I expect to have a response. Sometimes it would be several months. All in all, a time-consuming process, repeated every time I wanted to add a new gallery to those that had agreed to carry my work on consignment.
Some of the galleries I visited expressed a great deal of interest in my style and subject matter, but a comment I heard more times than I can remember was "A lot of our clients don't like works under glass. They don't like the reflections. Why don't you do these in oil or acrylic on canvas?" There were lots of variations on this comment, including one gallery who said they'd take my work, but only if I glazed everything with a product called Denglas, that had no reflections, and none of the 'fogginess" of regular non-glare glass. However, that product was five times the cost of regular glass, and I simply couldn't afford to frame my work using it, because as an unknown artist at the beginning of my career, I couldn't command a price for my work that would have covered the cost of the glass. And don't forget, even though I was paying for the entire cost of framing my work, the galleries still took 40-50% of the framed selling price. I had to pass on being represented by the gallery that asked me to use Denglas.
My advice to younger watercolor artists would be to find the galleries who fall in love with your work. When you do, they will be your best champions and salespeople. They will not ask you to change what you do. They may ask for more work in a certain size, or more of a particular subject matter that you already paint, but they won't ask a watercolor painter to become something else. If they do, keep looking.