[Kunama]

Greg, glad to see someone looking for advice first rather than telling a horror story and looking for a fix.
Depending on the amount of dust, crud or marks, you may or may not need to worry about washing the mirror.
Any dust etc will degrade the image but it takes quite a bit of dust before our eyes are able to see that degradation.
I have found that with my previous 18" scope washing the mirror twice a year was enough and it was being used without a shroud at locations where up to 2000 people were milling around kicking up dust.

My mirror cleaning method is quite simple and seems to work well.
I have a garden hose, a small spray bottle with a couple of drops of dishwashing liquid in warm water (not hot !!!) some isopropyl alcohol and 4 litres of demineralised water at the ready....
I place the mirror at a 45º angle on an outdoor chair out of direct sunlight.
I use a a low pressure stream of water from the garden hose to wash any grit and loose dust off the surface, usually for at least 5 minutes.

I then wet the mirror surface with the soapy warm water using the spray bottle and using my fingertips, very very lightly, feel the surface of the mirror for any deposits and keeping the fingers and mirror continually wet with the soapy spray. As soon as I feel anything, I stop and concentrate the spray on the spot till I can no longer feel the blemish. Do not rub the spot, if it does not clear with the spray, I use some isopropyl alcohol on a KimWipe and then rinse immediately.

Once the whole surface is clean I rinse the mirror with a stream of distilled water and leave it to air dry. Though I admit that to speed up the process I do use the corner of a piece of paper towelling to wick away larger droplets.

Fingertips are far more sensitive than cotton balls which can drag a bit of grit across the mirror's surface leaving scratches...

I don't soak the mirror in a tub, preferring to wash with a stream across the surface.... that way the grit doesn't stay on the mirror

( I have seen some people who claim dust has no effect on the use of a mirror, and upon looking into their scopes I would guess that due to the crud buildup the surface accuracy looked more like 1/4" rather than 1/4wave.... but each his own)