I am getting ready to apply a new elastomeric roof coating on top of the
existing asphalt membrane.

Instruction says to thoroughly clean and let dry before application. The
problem is the asphalt membrane has a lot of "loose" particles the size of
sand. I think it's part of the asphalt that is coming loose? I am unable
to clean them off totally. I can brush and brush and brush and more come
out and it seems to never end.

Any suggestions? May be I should just apply it as-is?

Thanks,

MC