Brush the skin side, cut side, or both? For larger tomatoes, are they better haved or in smaller pieces?

These are so, so good. And very forgiving. When I make them I usually just brush the top. I've also just put them in a ziplock bag with the oil and spices and gently shook it around. I would make sure to sprinkle salt on the top!

Regarding the size, the smaller the faster they will cook. I would say that the biggest priority is making sure your tomato pieces are all around the same time for even cooking. I've done this with cherry, plum, and roma tomatoes and they are all delicious... but the bigger the tomato the longer it takes!