I’m not sure what WGT means, however custom rigs for Roblox in blender is generally simple, you just need to use the plugin, this post isn’t covering custom rigs, just the R6 one I made, if you need help with making a custom rig, there should be multiple tutorials on Youtube.
It was an example video, but that video was just to explain exporting and importing rigs, it just went over other animation and animating weapons and such, but I referenced that video since it still covered exporting and importing, albeit not a lot, it still did.