You haven't said what variety the plants are or where on this glorious planet they are growing. But often determinate varieties will set fruit all at once. Are you trying to make something special?

Not really possible to do what you want. The trusses are very long on 100s and the blooms all along the truss are not the same age, same stage of development, not all ready to be pollinated at the same time, and so set fruit at staggered times.

The way it is done by commercial growers (whole stem ripe at same time) when you see it in the store is to harvest the entire stem while all still green and then artificially ripen them with ethylene gas. That's why they don't taste nearly as good.

"how often should I fertilize. Using organic tomato fertilizer."

No simple answer to that question as there are too many variables and we'd need to know all the details about them. The short answer is to follow the directions on the label.

Dave