using a rock rake

I got a rock rake to use on my various plots throughout,there are chert rocks about the size of a football.How do you use this thing,I have no experience with one.
I bought one when I first got started. Thought I could comb the field and clear all my rocks.

What a mistake. Used it once. It's been in my shed taking space for 8 years.

I think it is only good to drive up to one rock and pick it up then dump it