These were intended for single use, and were thus rarely made to be cleaned and reworn. Wedding dresses are fitted to the original wearer and often embellished with beading, embroidery, lace and trimmings. If the wedding dress is in good condition, with minor stains that you can tolerate, then a good dressmaker should be able to make alterations for fit.
Wedding dresses from the 1920s and 30s were usually made from satin backed crepe or other crepe weaves, whilst parachute silk was also used, if it was available, during the second world war. These are difficult materials to clean and may already be in a fragile state.
Common stains include grass, old champagne or white wine stains, food stains, sweat stains and possibly foxing (small brown stains) if the garment has been stored in poor conditions.
Old stains and soiling can be difficult or impossible to remove. It may be worth consulting a textile conservator in case localised treatment is possible. As a last resort, have the original copied to fit you by a skilled dressmaker.
Recommended book: The Wedding Dress buy HERE from the V and A shop.