I'd stop using the smith because it is way too easy for your dominant arm to take over in the movement. You could probably do a one armed barbell bench in the smith with relative ease. That just wouldn't work out well with a free barbell. I would try and focus on using exercises that prevent your strong arm from doing the work.
Pushups are probably your best bet right now. Don't worry about any swiss ball stuff or crazy variations. Just do real pushups to a set number. Aim for 50 or 100 and get to that number in any type of set/rep layout you want. After that I'd do some incline barbell presses with a pretty moderate weight. 12-15 rep range for these with perfect form and really squeeze the reps out. Three or four sets should work. After that hit a machine bench press. This will or will not work depending on the type of machine that you have. A seated bench press machine is the best choice, and most gyms should have one of these. Use this to do some one arm work. It will be a good gauge of your strength difference, and it's good for isolating that area. Again, moderate weight for 12-15 reps going to just about failure. What you should do is start with your left arm, and remember the number of reps. Then do as many reps as you can with your right plus negative reps to make up the difference. If there isn't a lot of difference just do five or six negatives per set. Do the normal one arm reps, then when you can't do anymore you use both arms to push the weight out but only your right arm to lower it. Only do this with the right side.
I'd also throw in some very very light rotator cuff work. These are ego killers so do them at home if you want. Use a five or ten pound dumbbell and really concentrate on the movement. Do these on a separate day too.