First off I am not a diabetic, but as a bodybuilder insulin is a tool we try and manipulate as much as possible depending on the cercumstances *fat loss or muscle gain*.
I prefer the brand optiumum nutrition,or now foods, though there are many other decent brands concerning quality and price.
Whey is the fastest absorbing protein in the bloodstream so i would be carful in combing it with carbs. It would be wise to use your glucose meter after a meal containing whey to see how it affects you.
Whey is not only type of protein power on the market. There are many types; including egg, soy and one of the thickest protien powders is called casein. Its slower absorbing in the bloodstream compared to whey protein. If your just looking for a bulker for foods i would acctually recommend this due to its thick filler potential in food recipies. (I think it also taste better)
Here is an explaination of whey i found from bodybuilding.com
"Out of the many protein sources out there, whey protein is the ultimate. It comes from milk. During the process of turning milk into cheese, whey protein is separated out. Protein can be found in a variety of foods -mainly meats, such as fish, beef, and chicken.
Dairy products as well as eggs, cottage cheese, soy and vegetable protein also contain good amounts of protein. Nevertheless, none of these sources compares in quality or ease of use like whey protein. Whey protein has the highest value in providing branched-chain amino acids, which result in building and retaining muscle tissue."
Here is some info. about casein protein
Micellar casein is the natural, undenatured form of casein found in milk. It is separated from milk by means of ultrafiltration, without the use of chemicals, which increases the amount of bioactive milk peptides that support immune function as well as enhance muscle growth. A property of micellar casein is that it may have the ability to form a "gel" in the gut. This provides a steady release of amino acids into the blood stream, which makes it an excellent choice for a long lasting anti-catabolic protein.
If you have any specific questions feel free to ask!