The chest works in 2 ways lower and upper chest ,Any incline workout will attack more the top part of the chest and e.g bench press and normal flyes or dumbell press will hit the centre of the chest and the lower part , Cable cross overs will hit the lower part especially but that exercise will be beneficial if you have enough muscle there. Any decline work will hit the lower part ONLY so doing bench press, flyes, cable crossovers and decline dumbel press would be the best way to go to add some muscle in the lower chest IMO

Jay