There were two types of dirt surfaces. One is just dirt that they treaten with used motor oil. This worked pretty good but it was a mess to get off of everything including your face and clothes. Mom hated it when we went to Langhorne. The other is clay and is different depending where the track is located.
Reading was sticky and Lindy dumped all kinds of stuff on it. Formula L is what he called it. They tried it at Flemington and it didn't work very well. They tried the plastic pellets.and that didn't work. The town complained and the paved place.
Tracks had used calcium cloride that worked great but they said it was a hazard material so it was banded.
Funny it is the same stuff they still use today on the roads when it snows and washes into the ground and or rivers and streams. Go figure.
I think Windsor had the best clay and I thinks they only put loooootttttts of water on it and just packed and rolled it.
Down hereally in NC the clay is red and they just use water and roll it. I got the same dirt in my yard as they race on, drys out quick and ain't good for much else....lol.