Rice stubble is the best, but the pattern of how you do it is the trick.
Say there's tall stubble around the pit, get chicken wire, bend it in a wavy fashion, go somewhere around the field, get whole root systems of stubble, and make it look like its standing up.
Say there's blowdown rice and the field was all cut on the ground, try and find a dry spot in the field, or go before they flood, take a rake and rake some of the fine chop and put a hefty layer on the blind.
Same for if the field was rolled, lay all the stubble in one detection.
One year we had a burned off field and it burned to the blind, we took black spray paint and painted the top of the pit, and just put a few pieces of stubble to break it up.
Someone might have better advise that works for you, but this is the way we've always done it and killed ducks.