You likely need to take some kind of light weight drag and pull across it just to scuff up the surface then broadcast some more brassicas or whatever you want to fill in with.
Plot would of looked better if you had variety in your seeds. Folks complains of poor brassica crops in live plants. But since your killing all vegeatation, other plants would of cooperated well with your brasicas. Pretty much never food plot withut atleast adding some clover in.