You do not need a designer for every social post, slide, and email. You need a small, clear system that lets anyone on the team make something that looks like you, and a designer only for the few things that set the direction. Most teams get this backwards: they pay for one-off assets forever and still end up off brand.
A lightweight brand system is not a fifty-page manual. It is the handful of decisions that, once fixed, keep everything downstream consistent: your logo in the formats you actually use, two or three colours with the exact values written down, one or two fonts and where to get them, and a few real templates for the things you make every week (a social post, a slide, an email header). All in one place the whole team can open.
You can assemble most of it from what you already have. Pull the exact colours and fonts from your existing site or logo files. Build the three or four templates you reach for most in whatever tool your team already uses, so people duplicate a correct starting point instead of designing from a blank page. The aim is simple: make the easy path and the on-brand path the same path.
Bring in a designer for the decisions, not the volume. The identity itself, the template system, a launch that has to land, anything that becomes the reference everyone else copies. Once those exist, your team can run the day to day. If you are paying a designer to resize the same banner every week, you have a system problem, not a design need.
Brands slip off course quietly: a slightly wrong blue here, a downloaded font there, a photo stretched out of shape. Two habits stop it. Keep one source of truth for the assets so nobody rebuilds from memory, and give the templates a quick review every few months to retire the ones people abandoned and fix the ones they keep fighting. Consistency is a maintenance habit, not a one-time launch.
The tool matters less than the discipline. A shared folder with the logo, colours, and fonts, plus locked template files, beats an expensive platform nobody updates. Pick something everyone can open without a licence fight, and put the link where the team already works.
Start with the single asset you make most often. Get its template right, then hand it to the person who makes it. That one fix removes more off-brand output than any style guide. When you are ready for the identity or the templates underneath it, that is the part worth a studio.