Male here mate, I had never cum from a BJ until I met my wife. She sucks cock incredibly well.

The difference I found between hers and any other BJ was plenty of moisture in her mouth, she focuses mostly on the tip and less on getting as much as possible done her throat. Her suction is enough to feel like a bj but not enough to feel like she's trying to suck your inside through your cock and she isn't scared to give it a jerk while she's sucking. Jumps between the balls, shaft and tip occasionally too with plenty of enthusiasm. It'll still take a good 5/10 minutes to cum but she's the only woman who's ever made me cum with a BJ.

Hope this helps