Solo founder, launched a niche tool for photographers. Struggling to get first users, how did you do it?

I've been building a client proofing and delivery tool for photographers and content creators for a while. Basically the client gets one link where they pick their photos, leave comments on the ones that need edits, approve, and download the final files. Works for videos too, they can comment at a timecode. The reason I built it is that almost every photographer I know does all of this in WhatsApp and it's a mess. "Which photos did we pick again?" is a message they get every week. Product