I germ seeds via paper towel method. After 3 days sealed in a baggie the beans will have a one inch or so white taproot sticking out of 95% of the seeds. About the only time I don't get 3 day sprouters is when I'm trying some bagseeds of unknown heritage.
Note -- when I put the sprouters first into dirt I bury the taproot but let the proto-leaves rest on the surface of the dirt. That way the s'ling doesn't have to fight it's way through a layer of dirt. Works for me.
Good luck, BigSteve.