This is an A1111 workflow outlining the secret to getting pro-quality images from SD1.5. No, it's not HighRes Fix + Ultimate SD Upscale. The attached PDF walks you step-by-step through this unique process and the results will astound you.

This workflow was developed by AIKnowledge2Go. A link to the original YouTube video is below. I've modified this workflow to incorporate the Tiled Diffusion extension which overcomes the issues with the Ultimate SD Upscale script.