when setting up a small compressor and garage paint.
where would be best place to have the pressure regulator and all the filters?

the compressor has the regulator and the gun came with one as well

should I use full pressure and have the regulator at the gun or other way around.

and has anyone used harbor freight oil separator and air filter

 

for a spray gun I always have it coming out of the compressor full force, and regulate it at the gun. I use the big harbor freight 30$ water separator and use an oiless compressor. Painted hundreds of things and never had problems caused by my compressor or filter

 

I have oil Compressor from harbor freight. The 10 gal 6 cfm and harbor freight hvlp also 6cfm
but last time i didnt know and only used red plastic air filter. Got oil bubbles under basecoat everywhere.
do i have to have oilless compressor?

 

I would get a filter, usually harbor freight stuff isnt bad and will work for the at home do-it-yourselfer.
Are you sure they were oil bubbles? Because oil usually causes fisheyes.
make sure to check your prep and use both a water based cleaner and a prep cleaner

 

It was liquid and looked yelliwish.
It was between primer and basecoat
And they show up after first freezing tempertatures which was about 2 months after painting