I did mainly planks. Followed the planks progression, from PB Fittness free e-book. But I thinks also anothers exercises that I do, like Pull Ups, Push Ups, worked my core.
But recently I am doing hanging leg raises and L-Sits and another gymnastic training and my abs looks more defined.
Avoid crunches at all cost, it is the worst exercise, with high risk of spine injury. Our spine is not designed to crunches.
The main work that abs do, is to stabilize the core and keeping us erected. So to train your abs properly, you should do movements that put more effort and force in stabilizing the core.
I can forward you some e-books with good progression for training the core. Just P.M. your e-mail.
P.S: You look amazing in the success story of this week. If I lived in Hawaii I would for sure go in a date with you. As you already know
Rephrasing the famous Socrates quote: "All I know is that I know nothing" and about that fact, I am still not so sure.
Greetings! from Jorge from Venezuela.