2D - Render Scene Secondary Textures to renderTexture

Basically, all my sprites have secondary textures like height map or normal map. What i wanna do is render them to a renderTexture to make some test shaders, but i have no idea where to start. I'm fairly new to Shader programming and only worked with it on small c++ projects for college, and a complete beginner with the pipeline in Unity, so i'm really lost here.