Is there a method that works best to polish off and make the bills clear?

30,000 grit or more sandpaper. Similiar to what they use on headlights. But I got to ask why ?

I have a collection of stained bills and also some repaired bills that have excess glue and smoothing to be done on

10~4 good luck.

I would try a Dremel with a buffing pad and some plastic buffing compound.

Yeah to the dremel approach.   Trying to do that by hand would get old quick.  A dremel would be a finesse power tool approach.  If you don't have one, go buy one.  That is one tool that every guy ought to have.

Actually its quite easy. I use mothers aluminum polish an an old T shirt.

 

Any fine polish like Flitz would work too.

If it's yellowing, it can be either a topcoat on the lip or the plastic itself.  If it's a topcoat, you can sand it off and re-clearcoat it by dipping it in a durable urethane.  If it's the plastic, you're out of luck.  If it's just scratches, they disappear when the lip gets wet.  Frankly, it's easier to screw it up than it is to fix it, so I just keep fishing them "as-is". 

Thanks for the ideas guys, got some dremels and a bunch of car care products to try out.

If it's yellowing, it can be either a topcoat on the lip or the plastic itself. If it's a topcoat, you can sand it off and re-clearcoat it by dipping it in a durable urethane. If it's the plastic, you're out of luck. If it's just scratches, they disappear when the lip gets wet. Frankly, it's easier to screw it up than it is to fix it, so I just keep fishing them "as-is".

I wouldn't say it yellowed but whatever happened it looks like it wad stained from a lure attractant

There's a product by Meguiars called plastx that's a cleaner/polish made specifically for plastic. Also scratch X works too.