Yes Quixel Mixer is great,
It is free for now and the learning curve is more of a straight away. Most users can prob. use it immediatly without looking at instructions.
Although it is very user friendly there are some things you will need to watch a video (which are good enough) but I recommend all who read this to try out.
Being able to adjust the PBR look by essentially sculpting it like a model is quite sweet.
While results will vary depending on the engine you are using PBR result looks good Skyline.
Funny, I mentioned Mixer to SP not too long ago.