what is the best way to strip the varnish off to do a bamboo resoration?

3M's Safest Stripper is the way to go. Pretty much everbody uses this stuff. Michael Sinclair recommends it in his book.
Just follow the directions on the container.

Andy,
The 3M product is good. I prefer Citristrip. It's available at Wal Mart and does a great job.

How old a rod is it? I never use stripper I always scrap the finish down to the enamal. There a boks out there on how to correctly repair and refinish these rods. I would becareful before starting this project you could be ruining a valuble rod. Have the rod checked out firdt. You might try Golden Witch for info.
Good Wraps Bob Andy you have a hidden email address

Andy,

I've been using CitriStrip for a couple of years now when I want to get down to the 'boo. I spread it on with a brush, and use a plastic bondo scraper to remove the finish/CitriStrip, rather than a hard scraper. I've never damaged cane using this method, and if you're careful around the wraps, you can preserve the original warps rather easily with this method. I've got a South Bend 346 in the shop right now for a repair/refinish, and I used this method to strip the finish off the rod, and managed to save at least 95% of the original wraps, the ones that weren't damaged to begin with. Works great, and doesn't leave a nasty smell in the shop.

Mark

Scrape it ! The best way to go , some strippers may soften or remove glue holding the wood together.