Been a lurker on here for some time, so I thought I would try to add a little for once.
I use Upper Hand Scents. They are an excellent scent that is very potent. I personally like the Hawg'n Garlic. I put approximately 1 tablespoon per 4 ounces of plastic. It remains very potent after your pour. The Bass Magnet Sauce is also a good one that will curl your nose hairs on contact. I've tried a lot of different scents and combinations of scents, but in my opinion these are hard to beat both on performance and price.
The link to the webpage is:
http://www.gobassin.com/bassscents.html
Make certain that you email him to let him know that you want the scents for pouring your own plastic baits. His formula for custom pouring is different than the field scent.
Good luck with your work station and watch out, this is an addictive hobby with many rewards!
Shawn