Trace your sun visor brim onto the paper. Test fit the contents of your buttons package on the drawing of the brim until you get it like you want it. Mark a tiny dot onto the sun visor brim where each piece will go.
Starting from either side, put a dot of hot glue where your mark is and apply the button piece that goes there. Repeat with each dot on the brim, working your way toward the other side of the sun visor.