I don't know why they're so popular. They suck (pun intended). I've been given plenty and they ranged from outright terrifying (too much teeth!) to just kinda meh. I'd rather get a handy than a BJ.
Best one I received she was did a lot of long licking with eye contact. It was sexy AF.
Edit: Standing up hand in the pants handjob is hot too.
It's all foreplay. Build up the tension. Tease. Enjoy. That's how you get good feeling blowjobs/eaten out/handies/fingering.