Legally it is not a problem as long as you create your own materials (drawing it yourself) and don't copy enteredentires pieces of works or certain characters (for example you can't use Mickey from Disney to your creations and earn money from it without permission).
Ethically, If you do not develop your own style and focus on having exactly the same style you will be criticised. It's ok to have his techniques as a reference, as long as it's only an influence on your own style and you can contribute with something new.
In short, Having influences is something normal and you shouldn't worry.