such as methyl hydrate Absorb the water then they must be removed by other means. They also may adversely affect the varnish and insulation in the transformer. I generally shy away from adding chemicals if there is a less invasive way. Heat was used in the manufacture of the transformer so all I would do is insure that the heat levels used were under those applied when the hot dip varnish was applied. Before I started to dry out the parts I would wash them off with clean water to remove mud etcetera. that got into the machines.
The pneumatics will have input ports and exhausts that were probably not sealed against immersion. Again I would use the same conditions that the pneumatics are expected to live with to drive the water out. Because there will be lubricant in the air passages you have a little longer to dry them out than you would have with exposed unfinished steel before rusting starts.
Terry