Draw a line between dirty and clean. Straw storage and soaking are dirty. Spawning and growing are clean. Wash hands and change footwear when you cross the line.
Use fresh straw that has not been rained on. Heat treatment must reach its temperature for its full time. DMR spawns in a room fumigated 48 hours earlier; a well washed and dried room with the door kept shut is the small grower's version. Space bags 15 to 20 cm apart on shelves so air moves.