Overstuffing

I have taken many an old sofa to pieces to find the understuffing was marsh hay, with a heavy over-stuffing of cotton, with no edge, but simply plain tufting.

Source: wiktionary

To remedy this, additional stuffing is pushed up under the overstuffing so as to crowd it out and fill up all hollows.

Source: wiktionary

Always use a layer of wadding or cotton overstuffing to make the work smooth.

Source: wiktionary