Going to Mexico in April, and South Africa in June. all i have are UV filters. When i had my kit lens & went to mexico, i bought a circular polarizer for it. i really had no idea what i was doing with it (why do you rotate it again?), so i didn't think much of it. do i want to buy CP filters for these trips? What about Neutral Density filters? I don't even know what they do. How would someone go about using a CP filter correctly?