MAS wood flour

Hi my name is Carlos 

This is my second time building the wood strip kayak but the first time purchasing Fierglass and Opoxy from Chesapeake. I purchased the MAS kit and I received some extra things like wood flour and cell-o-fill.  I haven't used these products.  I normally use carpenter's putty ( a mix of sawdust and glue).  I haven't found any Youtube videos to explain.  I'd appreciate your input.

Thank you, 

Carlos