I worked in the oriental rug business for years, selling and repairing them. I cleaned many old rugs, some that were pretty dirty, and the 1st thing you do is to turn the rug over, face down, and vacuum the back with a machine that has a beater bar. This beats the dirt out of the rugs foundation, i.e. the warp and weft. If the rug is wet washed before beating the dirt out, you turn the dirt into mud which gets into the foundation and when dried, turns to dry rot.