Here's what I do:

1. Load Vicki (or whomever)
2. Turn off IK (Traveler made some awesome utility poses to turn on and off IK for various parts, as well as white MATs and other things. Get them at Morphworld30.com.)
3. Load the body suit
4. Conform it to the figure
5. Starting at the neck and moving down, switch between your figure and your body suit, dialing in the same numbers between the two. In SOME cases, you might need to use a bigger (or smaller) number on the suit than on the body, but not much bigger. Do NOT forget the PBM dials like I did. I sat and pulled my hair out for 10 minutes trying to figure out why her legs were still popping out.
6. When your catsuit forming is complete, you can save it to your character folder (or export it as an FBM to apply to the catsuit, or just save the base PZ3, or.. you get the idea.)

Some notes:

1. There are parts of the catsuit that NEVER seem to fit right. The insides of the upper thighs are always a problem for me.
2. When you move the body, sometimes parts pop out a bit. The easiest way to fix this is to hide the part, BUT if it's a transmapped suit you will have to adjust a dial or load a magnet to expand that section a tad.

It's a pain the first time, but once you do it once and save it somehow, you never have to do it for that character again. ;)

If all this sounds like a pain, there IS another option. You can open up the character's MOR pose file (if it has one) and create a MOR pose based off that for the catsuit. You have to rename all the morph channels though, to match the catsuit. ie: breastsize 1 c vs. breastsize 1. Some people prefer text over fiddling with dials, which is why I mention it here.