I agree that a RCM is important, I beleive it's main purpose is to suck the crud fluid off the vinyl. So I feel that even more important for getting a record clean has to do with the brushes and fluids used. Some brushes are more effective of reaching into the grooves, and some fluids are more effective of loosening the dirt, mold, and whatever else lives on the records.
I don't know what brushes and fluids you use, but it might be something to consider and look in to. And again, a RCM for sucking up the crud can be easily made (DIY) for very little money and effort.
I don't know what brushes and fluids you use, but it might be something to consider and look in to. And again, a RCM for sucking up the crud can be easily made (DIY) for very little money and effort.