At first when my daughter wouldn't poop on the potty, it was very difficult to gage when she needed to, and to sit there long enough with her, but once I figured out when she had to go, I had to spend a few times with her forcing her to sit-(they say not to do that, but there was NO WAY to make her stay on there and go) so I would hold her down usually giving her a huge hug while she was crying, but using the hug to hold her down and encourage her, saying comforting things, and when she wasn't forcibly trying to wrestle off, I would sing songs and count and have her favorite books near by distracting her, and if she tried to hop off, I'd "hug her down" again and tell her firmly she HAD to wait until the poops came out, being very sympathetic, and sweet etc. I knew if I could just get her to do it a few times, she wouldn't be scared anymore. You're right, it takes forever, and you don't have time (I thought we would never get through it), but it's only temporary, she WILL get it. I was just about to start implementing discipline -even though they say NEVER do THAT-but there was simply no reason for her to try when she got nothing but praise no matter what, and she was pooping in her panties a lot. However, she suddenly got it and it clicked, so I never had to scold her etc.
At one point, she said through her tears while on the potty, "Is it good for my body?" Which is something I tell her when she's eating. It really helps her want to eat things when I tell her they are good for her body, so I said, "YES! IT'S VERY GOOD FOR YOUR BODY to poop, you feel so much happier and better, and you'll get big and strong with lovely hair..." For some reason, this really helped her to want to poop on the potty. "Now she'll say, I have to go poop, it's good for my body."
I know it's frustrating, but hang in there! She will get it. Definitely give a reward and celebrate when she goes-I'm sure you already know that. My daughter never gets sweets, but if she goes poop in the potty she gets dark chocolate m&ms, so that's fun for her too.
Good Luck!