Good to see your moving right along !

8" is a good starting point for distance from gun air cap to the panels you are spraying .

Not every painter sprays the same , some like alot of material coming out the air cap and move fairly quick , some like less material and move slower , its more of a feel type thing .
You just need to keep doing what your doing and keep playing with your gun till you find the flow of spraying .
Overlapping your spray pattern has alot to do with how the material will lay/flow also .
Spraying is a hard thing to teach over the internet.

On the DPLF sanding gummy is norm as it takes 72 hours to really get to where its not gummy when sanding . But spreading your body filler on bare steel is OK then spraying the DPLF over it all then spraying the K-36 over this is fine , so no worries there , just dont spray K-36 over bare steel as its not really required over bare steel as it doesnt have good metal biting qualities as does DPLF over bare steel then the K-36 .
Scuffing the DPLF with 80 grit is good enough , 36 is over kill .

Keep me informed on your process , and if you have a camera shoot me some pics , just PM for my e-mail addy

Spray