I use Frame Saver, but it is easy to get where I am at (USA), sold in several local stores. I have heard that linseed oil is also used, but if you use that make sure you do not store any rags where they could ignite, linseed oil soaked rags are subject to spontaneous ignition. I however have never used linseed oil on frames, so if you try it you might first research it on the internet.
When you reassemble, I noticed when I bought my Nomad frame that there was a piece of tape inside the head tube that covered the holes for the top tube and down tube. That was intended to prevent any water that came in past the headset to get in those major tubes, which I thought was rather brilliant. You might want to do the same. Also, put some grease on your water bottle cage bolts, especially the ones below the down tube if you have any down there, that can reduce water ingress from capillary action.
On the crank, sorry, can't help. I exclusively use square taper.