cst rcs calculation - Radar SSR f=1030 MHz. vertical polariz

Hi all,
I need to make some rcs simulation in cst and i am a beginner. The setup is the following:
Radar SSR f=1030 MHz. vertical polarization. Radar location is 5 km from a cylindrical structure on the ground (20 m tall, diameter 2m). The altitude of the radar is 150 m.
Earth curvature and 4/3 diffraction to be used for local incidence angle.
The questions are:
1)How can i calculate the incidence angle and than the X,Y and Z components for the plane wave on cst?
2)Which are the best options on the integral equation solver that i should use?
Please answer me,
Thank you very much in advance,
tommy567

Ok, i solved the first question, now i am just wondering how to simulate a coating (to simulate radar absorbing material) and show the rcs reduction. mainly i don't know how to cover the structure by such material