Creating background for my ballpython

[Python_Regalis]

I´ve really set my mind to making a rocky surface background. I will try to make it as easy to clean as possible.

No bigger crevasses for example.

I am not sure what to use for coating.

I was told to use, what we call in danish "Shipvarnish" directly translated. I think its called "Clear varnish" But still not sure what to use