I live just outside of Helen so I have carwash info. Heading south out of Helen on 75 (the main road through Helen), I reset the tripo passing the Circle K. Just so you know you are on the right track, at 1.2 miles you will see an open field with a gazebo sitting on a mound on left.
The first carwash is at 7.4 miles. This is a Chevron station with bays attached behind it. It has 4 bays, but last I saw, only two were functional.
The second carwash is farther away (9.6 miles from the Circle K), but bigger and nicer. If you pass the Chevron, you will come to a traffic light with an Ingles grocery store on your right. Turn left at this light and you will be on 129. Continue through the traffic circle and continue straight on 129 (aim for the McDonalds coming out of the circle). At 9.6 miles you will see the other carwash on your left just before the Sonic.
I hope this is helpful.