The Poopside of Parenting

We've been making a concerted effort to potty train our 3 y/o, Isla this week.  Actually, we've been doing the parental peer pressure thing for several months, as we look at having two children in diapers as only slightly less punishment than Purgatory.
It has been hit or miss. 
Last Sunday, Isla didn't want to eat her breakfast eggs, and said "I want to tee tee in the potty" as an excuse to get away from the table.  We called her bluff, and somehow that turned into a concentrated Potty Training effort that didn't exactly match my expectations for an "I'm off the grid" Mother's Day.
We had about a 50% success rate.
So, Monday, Ben offered to stay home with Isla, so we could put her through a Potty Training Boot Camp Day.  It began horribly, with her screaming she didn't WANT to use the potty, and crying for the ensuing hours.  As I am the weaker parent, I bailed to go to the grocery store.  When I came back, she was happy, and had used the potty several times.
BUT NOT TO POOP.
And, she has continued to refuse to use the potty for #2 all week, instead holding it all in, creating one, giant, compacted, uh...s%*t storm.  Last night, she woke up screaming that "It HURTS!"  Well, yeah, kiddo, I'm sure it does!
We had a similar problem with our first-born - something about the different sensation of going on the toilet that first time is terrifying to them.  We ended up using a water enema on her that STILL has me scarred.  But it worked.  She remembers it, though, and I think she'll probably use it against me at some point in her life.
So, basically, I am the worst potty training parent ever.  I dread the time so much, and I will very possibly consider ECing with this third child - in the hopes of truncating the whole endeavor.

So, that's what I've got - no pretty pictures of interiors, or plans of future projects - just preschool poop talk.  Any advice on getting us over this hump?
OK, I'll leave ya with this pretty toilet.