Here's a free Principled BSDF Shader guide to help Blender users, an extract from the free PDF guide and YouTube tutorial below, hope you find it useful :D : r/learnblender
Hands - PRINCIPLED BSDF by anul147 on DeviantArt
materials - How do I get transparency to work with the Principled BSDF shader? - Blender Stack Exchange
Principled BSDF for Physically-Based Rendering in Blender