Washing a vintage bike—special considerations? I've watched several tutorials on washing bikes, and the general gist seems to be to use a degreaser on the drivetrain, then wash the rest with soapy water, and don't spray hard when rinsing so water doesn't go into the bearings.  My question is are there are any special considerations when washing an older bike—in particular about rust?

It's also worth noting that my seat post has grooves cut out to reduce the weight, so water could potentially go inside the seat tube.  Should I take care to avoid this, or is it a nonissue?

The bike in question is a 1984 Trek 460, with a CrMo steel frame.
Cleaning a vintage bike isn't that much different than cleaning a new bike, with perhaps two caveats:


Vintage bikes are usually made of steel and the frame drain holes may be plugged or non-existent. I wouldn't use water directly (from a hose) directly on a vintage bike but instead only use wet rags and wipes. Don't spray (citrus-based) cleaner directly on the bike, spray it on the rag and then wipe the bike. While cleaning the bike, I'd see if there aren't drain holes at the bottom of the bottom bracket, chain stays, and front forks and make sure they're clear. 
Vintage bikes usually have decals that might be easily accidentally removed or damaged. I'd be particularly careful cleaning around these decals. If you like how they look and don't care about restoration value, I'd protect the decals by spraying them with a decal-safe clearcoat (or putting an overlay of helicopter tape) - but be aware that this will destroy their value for a conservationist, so do it if the bike is emotionally valuable to you, but not particularly rare (such as say, a 1984 Trek).