I don't know about Awlgrip, other than that you have to use a different approach than for other paints. For "normal" paints, like Interlux one part paints, I would suggest washing with a sponge and really good soap cleaner (eg. simple green) to get any grit, stains, etc. off first. Then I would use Meguiar's #45 or #49 cleaner/wax, which takes off a small layer of scum, oxidation, minor blemishes, etc., and then apply two coats of #56 wax. I don't have any interest in Meguiar's or any other similar products, but having tried most of the top brand names, I have had best luck with their products.
Other options to consider, depending on how bad the paint is, include:
1) Using a rubbing compound first, which is a bit more aggressive than the cleaner/wax mentioned above, if you need to take off more of the existing grime, scum, oxidation (chalky look), etc.
2) You could sand with 1,000 grit wet/dry sandpaper, then wax
3) You could clean, ensure all the wax and oxidation is off, then fill any small gouges and repaint (I have had good luck on previous boats with one-part polyurethane like Interlux Brightsides or Petit Easypoxy, which are easier than the two part paints.
Those are my suggestions, based on my experience, but others may have professional expertise or other ideas.
Frank.