What is the best method to clean IKO Armourglass Red Shingles. Small area about 8′ x 6′

In the first instance, a soft brush will help to remove excess dirt twigs, leaves etc.

The use of a pressure washer at a less intensive setting aimed down the roof (so as not to accidentally remove the mineral, or drive water up underneath the shingles) would be an effective way to clean the surface without using any chemicals. This may also help to remove moss and algae growth.