One more suggestion for "putting bus to bed":

If you can't park the bus inside a garage, try to park it on a paved
surface. If you can't, put down a sheet of vapour barrier (plastic 6 mil
sheet or typar house-wrap).

The problem is that a great deal of moisture comes out of the ground
which accelerates condensation and subsequently rust. The vapour barrier
should be laid such that air flows freely under the bus so that any
condensation that does form evaporates as quickly as possible.

Larry 
'86 Syncro Westy (used all year and never garaged)
'91 MR2 Turbo (garage stored winters)
'86 Subaru (garage stored most times)
'80 Saab 99GL (standing out in the open)