Did mine over the winter, no problem with the bleeder bolt leaking, but the water pump drain bolt did, just a small drip And only when hot. Triump has an up graded bolt with a larger diameter head. It's not stainless like the original though. You still need the copper washer.
Take the lower hose off the water pump and use a turkey baster to get as much of the fluid out of the water pump as you can.
I also flushed it out twice with distilled water and used engine ice for the coolant.
I bought a couple extra of the new bolts because they were cheap, if you want one I'll send it to you.