It is best to work a stain out from the opposite side or underside. This means apply the stain remover from the underside as well. Stain removal can be impossible on some stains, especially chemical stains that are caused by substances like furniture polish, bleaches, fertilizers, medications, cosmetics, dyes, etc. This is because many foods contain dyes or retain chemicals from processing. Today's fabrics are more complex and many synthetic fabrics have chemical finishes.
Many stains are difficult to remove.
Do not expect an instant miracle. Time can be your friend. Repeating the procedure may be necessary. Sponge with cool water. If stain remains, sponge with rubbing alcohol or detergent.