I have not used it but just bought a spray can of Deoxit. From reading
about it, it seems to be the greatest stuff for cleaning contacts.

I have an old Tectronix Scope 465B that one chanel has a flakey input
switch. The manual says only to use isopropal alcohol to clean it
with, I did that with some 99% and it helped some, but thinking of
using some of the Deoxit on the switch. Would that be ok or not.

I would hate to mess up the switches as they would be almost impossiable
to find replacements for .

First recommendation would be "stick to the manufacturer's
rules". They may know something we don't.

I've read a number of comments (Hi, Jeff!) that DeOxIt is *not* a good
thing to use on gold-plated contacts. Gold plating is often somewhat
porous, and the DeOxIt can creep through the pores down to the base
metal and may actually attack it. This can cause the gold plating to
fail.

CAIG makes a different product ("ProGold") which is intended for
gold-plated contacts, and if I understand correctly, it's intended to
avoid this problem.

Your Tek's switch may actually be suffering from contact wear, rather
than contact surface contamination. If I recall properly, the
delicate contact fingers in the switch do "rub" slightly on the
contact pads when the switch is activated, and over time this can wear
away the gold plating, and the contact don't work well after that.
Cleaning (with ispropanol or anything else) isn't going to help this
situation more than very temporarily.

I haven't found a solution (so to speak :-) ) for this sort of
problem, other than an actual repair of the switch (replace the
contact fingers) and as you note, this may not be possible due to lack
of available parts.