does any one know what a good substitute for duncan hines is? i need to buy in bulk.

This is a good question, I wish I knew . I am under the impression there are a lot of bulk cake mixes out there but if you are a DH lover nothing compares.

J M Smucker Co Elyria, OH
http://www.smuckers.com/
440-323-5100
Manufactures prepared cake mixes.

Imcb Corp Bonner Springs, KS
http://www.vcponline.com/
913-441-6310
Manufactures prepared cake mixes.

You may also contact local wholesale food companies in your area and ask about the commercial cake mix products they sell, which is most popular with commercial bakeries in the area. You can also contact the brand product you use, there is usually a 1-800 number on the box and see if the product is sold for commercial use.

If you are interested in making your own bulk cake mix consider Make-A-Mix by Karine Eliason, Nevada Harward, & Madeline Westover.
http://books.google.com/books?id=ORlzA7NJY-wC&lpg=PP1&dq=make%20a%20mix&pg=PP1#v=onepage&q&f=false

You can also Puchase The Culinary Institute of America Baking and Pastry Mastering the Art and Craft for bulk cake formulas.