How many hours to block sand?

LOL crap I wrote that and thought you were clearing the car. You were speaking of Primer. You just want to knock down the orange peel. I actually just used a green brillo pad and did it to my car. You basically just want to knock out the over spray and then any really rough spots. I think I spent about 2 hours doing my car.

For the clear read below

For the Clear Coat I literally just did this, this past week. I spent a full 2 days and those were good 8-10 hour days. I could have spent at least another full day on it. It all depends on how well you want it to look. I still have some very minor orange peel in mine. After the 1st round of 3 buffings I can make out definitions of lights, although a tiny bit wavy. Im not going for show quality. I want nice a nice driver and being the fact that I did everything myself and didnt spend 10k on a paint job Im ok with the way its turning out.

Again its all how well you want the car to look but plan on spending at least a good 2 days.