I use manual. I was trying over winter to do it once using snow as the white and it still wouldnt work for me.
how so?^^^^ i would like to know how to adjust the WB preset, settings as well....
Hmm, never thought of expanded polystyrene (EPS). I extrude, expand, and mold expanded polypropylene (EPP) and polyethylene (EPE) for work, but not polystyrene. I can tell you that the shades of white in EPP and EPE are as variable as the shades of green that you see in different grasses due to the various amounts of additives we put in the plastics. That's a bummer. I see more EPP and EPE in a week than probably everyone here sees EPS combined in their lifetime, LOL.White polystyrene foam ("Styrofoam") cups and plates work very well for white balancing. You can either use them like a white card or like an expodisk (but for white balance, not necessarily for exposure).
Polystyrene foam is spectrally neutral by nature - more neutral than many commercial white balance targets. Plain white paper kitchen towels tend to be good targets as well - they usually don't have optical brighteners. As an aside, that makes paper towels useful as neutral diffuse reflectors.
PS Here's a link to a little note I wrote about white balance targets.