The amount of gourds produced on a plant depends on several factors.  Including the soil's fertility, length of growing season and amount of sun and water the plant gets.  The smaller varities produce more per vine that the larger ones.  Small gourds varieties are picked prior to the first frost. When their stema are dried out all the way back to the vine.  Where as larger gourds are picked after the first hard frost, or when the vine dies and the stems on any gourd is dry and brown it's ready for picking.  A gourd is ninety percent water when picked  and can weigh fifty pounds or more for some of the largest ones.  Once harvested all gourds can be washed in a mild solution of one cup bleach to a gallon of water solution.   Then allowed to dry out completely.
 One form of gourd cleaning is done on the "green"gourd prior to drying.  The skin  of the gourd is scrapped off with a butter knife  (smooth dull blade)while it's still  green.  Then the gourds are washed in the bleach and water solution mentioned above once every few weeks for the first month or more of the drying process.
This is to keep them from molding so when these gourds dry out they'll have a lighter cream color. 
 Drying gourds need to be in an area with good air circulation in the garge or out on a deck outside.  Because drying gourds give off a slight  odor as the epidermis molds off.  But when   you've got a whole bunch of gourds to dry in one area it can be a bit much.  I use long narrow  two by four benches with hardware cloth tops.  Or I drill a small hole through the stem thread a small cable tie  through make a loop and hang them from the rafters in the garage for the winter. Try to keep them up off the ground away from small creatures like mice who chew holes in to gourds and nest for the winter.  While gourds dry out the skin begins to rot and mold this is normal and the patterns that are left can be very attractive, almost like a bural wood.  Of course you could just keep a few washed in the bleach and water to keep them from mold every few weeks for a couple of months.  the  epidermis remians rather waxy on the gourd and can be left on or sanded off when drying is complete.  A gourd can dry out in four months for some of the small ones and a year or more for the largest ones.  The general rule is when the seeds rattle inside it's dry.  Or it's very light when you pick it up.