Looking for help getting started on creating an IN-GAME drawing system

What the title says – I’m looking for a tutorial or starting information on how to create an application that allows for painting/drawing on 3D models in-game. All the searching I’ve done so far pulls up results to do painting in the editor.

I believe you’ll need to find your nearest vertex to your brush, find its UV coordinate(the same point on the texture2D) and then you can use set pixels.