If by "initial training period" you mean that you've just started working on it, I'd go with diapers. Or maybe Pull-Ups, which I hate and think are from the devil, but they do have their time and place. Pull-Ups would seem different if you're worried about confusing.

It's been a while since we did this with DD5, so my memory isn't perfect, but we went back and forth between diapers and underpants a lot, and she was pretty well trained by about 28 months. (Extensive summer traveling did bog us down, but I know other families who were more dogged in their efforts to keep it going while on the road.) Actually, she was trained before that, but she decided to take a break once she'd mastered her new skill!

But if you mean that most days are dry but you have an accident here or there (less than once a day), I'd go with extra outfits. Ya gotta do it someday. If you're worried about someone soiling your friend's new Turkish rug, maybe hold off on the visit instead!

Also, some people stress less about accidents than I do, so they may give you different advice. I am not good with messes! (Except those of my own making, like my office, kitchen, bedroom, etc.)

Shaun