I read somewhere that a person can add talcum powder to oil based polyurethane as a flattening agent. I was wondering if this was a bad idea. I tried it on some scrap wood and it does mix into the poly and doesn't make it cloudy. What I don't know is what it would do to the long term duribility as compared to the proper flattening agent. Where I live I can't get flat polyurethane or the proper flattening agent either.