Actually, *my* chest workout might not be suited for you as our goals are a bit different. I never really do anything for lower pecs, rather concentrating on the upper and inner parts where you can never have too much thickness. The exercises that I normally choose from are : (in no particular order, just what I feel like doing and what equipment is free)
One arm pec dec machine - doing these with one arm will allow you to cross the arm further across your body and get a much stronger contraction. I often like to do this first in the workout. That way it pumps blood into the area and helps "pressurize" the muscle before I start with compound movements like presses.
Incline presses - regular incline bench, but also I like to place a bench inside the power rack and tilt it 10 degrees up and do presses that way as well. Same with dumbells.
Incline HS Machine - I admit I do not use the standard one (weird movement for me) but there is ONE in particular
http://us.commercial.lifefitness.com/content.cfm/iso-lateralhorizontalbenchpress
Like that one, but slightly a bit more inclined
that I have only found in two places, neither which is here in South Florida. That machine is the fucking boss. I would join a gym simply for no other reason than it had that machine. (if there was one here that did.)
Flat bench presses to the throat - these are another favorite of mine which actually yields consistent results in everyone that is faithful to them. You can't (and don't want to) use a lot of weight. But I scoot down the bench some so the bar doesn't hit the supports on the movement plane. I hold my head back and flat on the bench. None of this "neck crunch" to look at my chest or bar while doing the movement. I lower the bar all the way down to touch my adams apple and then push it slowly back up to about 2 inches short of lockout. I don't lock out. And I don't go heavy. I am usually using 385 for 7-10 reps on the flat bench regular presses (when the rare occassion presents itself that I do them) but on this movement, I never go over 225. Forget the weight and instead slow the movement down so you can feel every bit of stress in the muscle and focus on your upper chest stretching and pushing.
Flat bench medium grip presses - Not a regular bench press grip, not a close grip. But in between. Much like the exact same space between my thumbs as there would be if I were pressing dumbells and had just completed a rep. This is a terrific movement for adding inner chest thickness.
I do various flyes, cable cross overs, etc.. as well. Something to throw in keep the boredom away.
Now regarding your request for lower chest development. Continue with the decline presses, keep your reps about 10, 4-5 sets at the start of the workout BUT make sure you lower the bar as far down as you can. Try to get that bar all the way down to your upper chest / neck. You will use less weight, but you will not lockout and thus the stress multiplies each rep.
Follow these up with 3 sets of a superset of dips - keep the elbows AWAY from the body, upper arms should be parallel to floor at bottom of the movement with your elbows sticking out to the sides. Much like an old west gunfighter in "position" to make a quick draw during some High Noon showdown. Hit 10-15 reps, then hit cable crossovers. But do not do them the regular way where you take the handles and step forward. Instead grip the handles and don't move. Stand in the middle of the machine and bring your arms down to your sides. It will sort of resemble a bird flying. Up and down. This will focus on the outer pec area and help give the illusion of lower pec thickness.
Also try other machines in the gym until you find the one that helps you "groove" to the muscle pathway and gives the greatest benefits. But don't discount the importance of continuing upper chest work. Throw in at least 3 sets of something for that area while you are prioritizing the lower area.
(sorry about my description at times, I know some of them make no sense. You have to actually just stand up and try them to hopefully get the idea I am trying to convey.)