First, you need a prop that is for glow not electric, APC is what I use. There is a prop size range for all glow engines. If this is a new engine you need to break in the engine with a recommended size prop.
Two, a spinner for a .25, if you look at the specs on the engine it will tell you the shaft size, get on tower hobbies and look for your engine and it will tell you the shaft size and when you look on the web site that your going to order it will tell you the size the spinner will fit.