Certified GKH Gardening Expert
This can help the productivity of the fruiting branches. You can increase productivity with any of an array of "bloom boosters". This is just a mix of very large amounts of highly availably potassium and phosphorus. There are many types from many brands, and most are exactly the same thing. For the most bloom control, avoid any of the booster with nitrogen unless this will be your only fertilizer.
I recommend starting out using only at 1/4 strength, and slowly moving up as you see fit, and if they seem to handle it.
Add dolomitic lime to the soil as well. This will provide calcium and magnesium, as well as keep the pH stable. It will save you quite a bit of trouble in the future with tomatoes in container.
And, as always, tomatoes are LIGHT HOGS... Give them as much as possible, but keep them watered in container. An occasional dry out is healthy, but keep an eye on that.