I do the banana trick almost every time I have access to diapers and I find that very green bananas work better than frozen because they tend to be harder.
I just find a relaxed position, relax all my muscles, use a bit of Vaseline or lube and shove them up. I can usually do 4-6 and then once I get the diaper on, I'm already having trouble holding them in. I find for me it's the mere feeling of really having to go that makes it come out and the longest I held it was two hours, before I fell asleep.
I woke up as they were coming out and couldn't hold them in, it literally felt like I was involuntarily filling my diaper with the real thing. If you go before they've been in long, but have had long enough to warm up, they feel like a more solid poop. Plus with their size, you're guaranteed a huge load.
I prefer it to the real thing because I can sit around with a big load in my diaper without the smell, and no one ever knows but me.