You can certainly use any store bought curry blend you like, but the one I use myself is my own Madras-Style Mild Curry Powder.
It's very important to have everything set up and pre-measured for yourself before the greens hit the pot. We are not cooking them to death like is usually the case, and things will move fast.
Don't add salt to this until you are ready to serve it, as it will make the greens weep and get watery. The sour cream makes things just thin enough and the salt will take it overboard if the greens sit in it.