I'm the man in the equation, for the record.

-You just haven't found the right videos, I suspect. That being said, for most people titfucking isn't the "entree" of sex like it is for me, it's more of an appetizer or side dish, so for most porn they're just going for the more broad appeal finishes, I assume.

-Any position? Usually it's her on her back, me straddling her waist. But I'd also cum in tons of other positions, including me sitting while she kneels and serves me, reverse titfucking while she lays on the bed with her head over the edge leaning back and I'm positioned over her head, and more.

-My current partner has very large and soft and "pliable" boobs, so it's fully enveloping like a cushion. But I've titfucked multiple women with different kinds of breasts. In general as long as there is going to be pressure around my cock it's going to feel good.

-Yes, of some kind. Tbh often just a healthy about of saliva (after thoroughly tongue-bathing her tits) is enough, sometimes with a spit or two during to keep the wetness going, but actual lube is sometimes used as well (just a little bit is usually needed though). Better than lube though is either baby oil or olive oil.

I don't have easy examples saved on hand, I'm sorry, but searching "finish between tits" I've found helps my searches get what I'm looking for.