How much sanding is enough? Just would like other experiences. I think I will sand another 5 or 6 days on my 68 - spray it again with color build primer and sand another 5 or 6 days.

Currently using 180 grit will go down to 400 before the top coat is applied.

That silkens color build is expensive - 3 bills for one gallon plus the additive(probally 2 gallons of paint). Just to sand it off!!!

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68SS ZZ4, 4sp T-10, 12 bolt, getting painted

78Z28, 330hp vortec, TH350, 10 bolt (just finished)

I don't mean sound condescending, but I think you are talking apples and oranges when dealing with your prep. The amount of "days" you spend on any job should not matter unless you call a day 8-10 hours. You should do enough work to complete the job correctly. With that said, you should talk to your local PPG or Dupont or whatever brand you plan on using to get instructions on what products to lay down and in what order. You will also want to tell them what surface you will be applying it too, ie. old pain or bare metal. These are critical questions if you are to get a nice paint job and not waste time and money....Good Luck

Are you using guide coat when you are sanding? If you are, you know when the guide coat is gone and you are not hitting high spots, (which are bare metal) you are done.

Not trying to sound like a smart A$$ but if you want a nice paint job then take your car to someone who knows more about it. Sanding a car is the main part because if it's not done right your paint will look like $hit. Trust me, I sand cars everyday.

If your sanding primer, the 1st coat you should of used something along 120 grit, and then primed it up again and used a board with 320 grit. Trust me, I too sand cars every day.

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67 Camaro SS Conv.
70 Challenger R/T Conv.

I usually wetsand with 320 or 400. I think if you have to go any lower, you must have a cheap paint gun or you're not dialing the gun right. The prep work is what makes the difference between a show paint job or Earl's.

You want the body as smooth as possible because any inperfections such as roughness of primer or deep scratches will stand out after paint is applied.