My first tip is always a high build automotive spray-filler.
If that fails I use Bondo then hit the prop with an orbital sander.

This is more a body shop tip than a 3D printing tip, but if by Bondo you mean the two part body filler, there is also a one part "spot putty" that comes in a tube. It's designed to fill small scratches/dings in body work after the car has been primed. It's a fast drying putty that is a LOT easier to sand than the two part epoxy body filler. You should be able to find it at any auto parts store or any other place that sells the regular Bondo.

The sanding properties are similar to sandable primer fillers. The idea would be to spray your part with primer first, then if it looks like primer alone isn't going to be enough to fill the imperfections, touch it up with the spot putty and let that dry before sanding. About the only trick to using it is that because it is very fast drying, you need to apply it quickly, then not mess with it until it dries.

Another auto body trick you might find useful is "wet sanding". I had a flat part that was coming out kind of scruffy looking with dry sanding, even with acetone treatment after sanding. It looked like the sandpaper was clogging up and laying down deep scratches in the surface of the plastic. I took some wet/dry 240 grit, put a strip on my sanding block (available at auto shops for around ten bucks), and did my sanding under a trickle of water at the kitchen sink. It did a nice job and it's easy to see where you are because the imperfections in the plastic show up shiny. When the shiny places are gone, you know you have it perfectly smooth.

Hopefully some of the above is useful information and/or leads to other ideas that may be useful.

As to the small details, I'd suggest going very light on the spray in those area's.
It is afterall a high-build material so it will clog up bits or run if sprayed on too thick.
Maybe the move would be to tape off the detailed parts until you've got the big round area's flat then hit the small area's with as little as possible.
Just be prepared to do some sanding though.

Other than that, just standard spray can operation should be fine, multiple coats and even distances etc etc.

The facebook link in my signature contains many photo examples of this process if you scroll down a bit.

I recently had a Pip Boy from the Fallout series printed, and the piece has A Lot of print lines. I'm just wondering the best way to get rid of them , without using a vapor bath.

I've sanded it down a bit, but the lines are still there. I'm planning on painting it, would a filler primer be ideal in this case? Can I use some sort of sealant, like modge podge, for example; to fill in the lines and sand that down? I'm at loss and am unsure of what to do here. Any suggestions would be so helpful! Thanks so much!