Compressible Navier-Stokes with Non-newtonian viscosity in PDE module

Hello,

I am new to COMSOL and I've been trying to model some incompressible Navier-Stokes system with variable viscosity, a Carreau viscosity to be specific. I have used the CFD module to model this with the single phase laminar flow which also has Carreau fluid properties, and now I'd like to use the PDE module, but I have no idea how to input the equations.
I have also seen there are several ways to do it: Coefficient, General and Weak forms. I have my Navier-Stokes equations in cylindrical coordinates (better for a pipe flow) and in differential format, so my question is what would be the best way to do it and how?

Thanks in advance,
Daniel