Earlier this year I was fortunate enough to meet up with @digit in Gainesville Florida where he very graciously provided my wife and I the opportunity to do some matrix fossil hunting in a local stream. We sieved for a good long time collecting many nice shark and ray teeth as well as other items out of the large portion. At the end we nearly filled a five gallon bucket with gravel that we ran through essentially window screen in the creek to get out the silt and clay. My original trip report can be found here:
http://www.thefossilforum.com/index.php?/topic/114209-north-florida-