How (or if?) to divide new veggie sprouts

I decided to start a bunch of seeds left over from last year.  Being at least a year old, and not stored carefully, I assumed many would fail.  So, I planted the old ones 2 or 3 to a hole to improve my odds.
To my astonishment, the germination seemed to be as good as last year's.  The seedlings are out of the ground about a week, so still lacking true leaves. They are looking good to me.

My question is, what do you do with veggie seedlings that are packed into cell-packs?  Like 3 tomatoes growing out of the same planting hole?  Is their a way to extract one or 2 of them and replant?  Or do I let them go for a bit, see which appear to be going the bets, and snip off the others?

I personally have plenty for my own garden needs, but I have some really good stuff I would love to see go to a good home (a number of really delicious heirloom toms, peppers, eggplant, brocc, kohlrabi...).  I would be find doing the work separating and replanting them.  I've just never done it, and have no idea if it's possible, or what kind of success rates I should expect.

I'm very glad this site as a gardening for beginners section!  I always grew from greenhouse seedlings, and only in the past couple yeras tried my hand and starting from seed.  It's a lot of fun.  A little nerve wracking--I was slightly too cool, so things were considerably slower than I expected. I was ready to dump the whole project, and then they started popping.  I guess, Mother Nature takes as long as she takes.

I have great success with using a chopstick.

I tend to try to get to the seedlings soon after they emerge so there is less root mass dividing into hairs. I will take my chopstick and gingerly tease out the extra seedlings and then plant them into a new cell.

I fell into the "Ohh these tomato seeds are old, they totally won't all germinate" and then had a HUGE garden of tomatoes that year. It was awesome because I grew a blend of heirlooms and found what worked best for my environment.

If you don't care to save all of them, I'd tease out the weakest and leave the best growing.

i do it once they’ve got true leaves, pulling gently apart, holding onto the the stems.

Tomatoes are not delicate. I find that if it germinated, it will transplant easily, even if I just gently pull it out of the dirt by the stem. I usually end up with random tomato plants stuck in random bare corners of my property that I couldn't bear to throw in the compost pile.

I also wait until they have true leaves for the toms, peppers, eggplant.

When I direct sow beets and turnips I plant 3 or 4 in each place. Elliot Coleman does this. As the plants grow, the bulbs push each other apart. As one gets big enough for your purposes, harvest it, leaving the others to get bigger. This should work for kohlrabi and other bulbs.

I don't know about broccoli as it hasn't grown well for me.