how do you attach eched parts.

You can use CA glue (Crazy glue), or I use a glue call Gator's Grip Glue. It's an acrylic glue that gives more time to get the piece in place before the glue dries.

Hogfanfs covered it well. I've used loctite brand super glue. You'll want the thin for quick gluing and the gel for when you want some working time. I just bought a bottle of the Gators Glue and so far I really like it. Allows for a lot of working time which I need:)

DITTO !  T.B.

I use CA as well, usually thin and thick viscosities. I apply using a homebrew applicator that anyone can make. It is basically one of the larger sewing needles with the end cut off of the eye leaving the two prongs. The prongs hold the ca until they touch the surface to be glued then it releases into the part. Leaves some pretty clean attachments.

Gator glue.

This thread should probably be in one of the other forums (techniques, maybe). 

I and many of my ship modeling buddies use thinned white glue.  The small size and light weight of most PE means you do not need a lot of bond strength.  White glue dries slowly, giving you a lot of time to position piece, and thinned white glue leaves a pretty unobtrusive mark if glue runs out of bond area.

For large pieces like a long area, like long railing lengths, I will put down a couple of small CA spots just to hold the railings in place while I run a bead of white glue along the railing/deck bond line.

Great idea with the sewing needle. Thanks!

I also use a needle cut off to make it into a fork. I made two- one for the CA itself and one for the accelerator.  Some of my buddies ask what happens when it gets a CA buildup on them.  Because those things are made with stainless steel, the CA does not stick that well to it, and I clean them off with an X-acto knife- no problem.

I have been using Aleenes tacky glue. It grabs super quick and dries clear and invisible. It has a strong bond too.