I don`t see what the reason is why you dont like wetsanding factory paint.
Wetsanding with paper that is made for it, on a hard rubber block, actually works really great, fast, and the water dripping from a hose (that has the metal end cut off), is continually cleaning the work, so you don`t have to keep rinsing it to see what you have done..
The sand paper will last a lot longer and be more efficient if it is continually rinsed with the water..
The block is necessary to insure you sand "flat" so the finished painted panel is also perfectly "flat"..
This process with a very light guide coat of something like spray can black lacquer, sprayed over the work, will absolutely help you "see" where you have sanded, and where you need to sand perhaps more. The guide coat will also help you see high and low spots, which you want to make "flat"..
Yes, your trained, bare, clean, dry, hand can also with practice, also detect high and low spots, etc., but in production, you have to be efficient, fast, and do perfect work each time..
This is how I prepped a zillion vehicles when I worked as a Painter in a couple of shops before I painted them..
Dan F
)