Lyra is an amazing resource, but it’s a little dense for new developers. You’re learning to swim in a deep lake in this case, as because Lyra is set up for online multiplayer. This makes everything you do significantly harder.
That said, there’s not many resources directly for changing the materials on Lyra guns with information from elsewhere. This BP I showed off before will change the material, but you need to decide where you’re going to get that material. I can do a slightly longer write up and go into detail if you’d like, but it may take some time.