Help choosing the right type of paint

I'm in the process of finishing my garage and am just about ready to begin painting. Got the first coat of primer finished today and will be laying down another coat tomorrow. I've been doing alot of searching on what type and finish of paint to get for my garage and am looking for some help/information. I went into my local HD today and finalized my color selection and picked up a sample of each color. Unfortunately all the samples are a flat finish. Here are my questions:

1. Interior or exterior paint?
2. Satin, Semi-Gloss, or Gloss?
3. What to use to prime and paint concrete lip?
4. What is a economical yet decent looking trim piece to use as a border?

I am finishing the garage with the main goal of starting up and operating a small auto detailing business out of it and would like to also get into woodworking and possibly welding in the future.

The paint job is going to be a two-tone with a light grey bottom, darker grey trim piece or stripe with white on the upper portion of the sides and ceilings and a blue upper portion on the back wall.



Here's a picture of the cement lip I refer to, not sure what to call it. It sticks out a couple inches on the back and exterior wall but is almost flush with the interior wall.



P.S. I've been working on the paint scheme ever since I started the project and a big thanks to EMC2 for the inspiration to finalize it.
http://www.garagejournal.com/forum/showthread.php?t=181620

You would be ok using a indoor latex paint. To help reflect light off the ceiling you can use a gloss white and for the walls i would use a semi gloss or gloss. The semi gloss and gloss are alot more durable then satin and flat paints so in a garage where you might get something on the walls then the semi gloss and gloss will clean up much easier. You could use some primer called Dryloc on the concrete lip and it will seal it from moisture and then paint with what ever color you want then.

1. Interior or exterior paint?

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I used exterior. I hose down the floor and it is a "workshop" not a "showroom" so it seemed the extra durability was worth it.

2. Satin, Semi-Gloss, or Gloss?

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Semi-gloss at least. It will be more resistive to dirt and such.

3. What to use to prime and paint concrete lip?

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Get a "block filler" primer. It is thicker than regular primer and fills up the pores quickly. A regular primer and you'll be using multiple coats.

4. What is a economical yet decent looking trim piece to use as a border?

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Basically a chair rail type trim? I'd go with a fairly simple piece - maybe rectangular with just rounded edges? I doubt you want anything too fancy.