Nobodies, I like the can and bell ideas. There are times it seems like they are trying to let us know they need to go out, but it's hard to tell.
We had been using treats when we took them out, but that got inconsistent. We will be getting back on that.
We keep them in the crate, at night, and they can both hold it all night. So I know they are capable of holding it in.
We recently started putting them in the crate while at work. They usually aren't alone durring the day for more than 4-5 hours tops. Seems somehow cruel, but until they stop going in the house, not sure what else to do.
When we're home we let them outside every hour, or two, at the most.
I take them for one good walk 45-60 minutes (depends on how fast I feel like walking) 5-6 times a week.
Read this book. Got some pretty good tips, but it doesn't really cover potty training.

They're good dogs, 98% of the time. Just need to get them over the potty training hurdle.