Sheri, it's possible you had different types of worms on the various plants, too. The really huge ones that you found on your tomato plants are probably tomato hornworms or their close relative tobacco hornworms. They can exfoliate a tomato plant in just a few days, and yes, they get as big as your finger.
Gardening is a long, steep learning curve. Don't give up, come and ask us for advice sooner! I'm with Sandy on the Bt being the "magic bullet" here. You don't want to just go trying stuff until you've killed them all off - some of that stuff like Sevin is not rated for use on edibles if you're trying to stay organic. Baking soda is good for fungus prevention, and soap should be used by itself, not with oil. Oil is good for smothering insects like scales. Soap kills on contact most sucking insects like aphids and whiteflies. Both of those can make the sun burn your plants so rinsing them off again in the morning is a good idea.
But with the hornworms, just get out there and pick them off by hand as you have been. They're so big, it's easy.
Btw, birds love to eat caterpillars - since I put out a birdfeeder near my veggie area, I've hardly had any problems like this at all.
