You really only have to worry about the plastic. Brett is not a bacteria or a fungus, it is a yeast. Albeit a little more hardy than sacchromyces, but a yeast nonetheless. For the glass and stainless steel, a hot PBW soak followed by star san should do the trick. I would use seperate poppets, tubing, and plastic/rubber for your Brett and non-Brett beers. Boiling should kill the Brett, but I would just try and keep everything seperate for peace of mind. Boiling sanitizes, it does not sterilize. You need pressure AND heat to sterlize, i.e. a pressure cooker. If you have access to a pressure cooker for the small parts, this would be better than boiling.