I'm more familiar with the other end of Washington County - Scuppernong Township, and where the records of St. David's Episcopal church do include marriages of slaves (which they referred to as servants, instead) of some of the more prominent slave owners, it appears that the majority of the slaves were those who attended the church with their masters and mistresses. In other words, the house slaves. The St. David's register is chronological, with no separation of the colored and white marriages.
Interestingly, the McRae surname is one of the names for the woman that I've been helping. Sherrod McRae, who was the last male of his line (he had daughters, but no sons), not only owned quite a few slaves in Washington County, but he also owned a saw mill where he hired slaves from others. At least one of his daughters ended up living in Martin County, and that could be how Willis McRae ended up with that surname.