I've switched over to the new "Pink" ultralight spackle. Cheaper and lighter than hobby shop balsa filler. Also, it goes on pink and stays pink until it is dry enough to sand, when it turns white. I'm using "DAP" brand "DryDex", but Red Devil and Elmers are selling similar products.

1/4 of an inch is a big gap to be filling with any kind of filler though. Filler has just about NO structural strength.