Get a bucket and a brush to wash the bike with.Pressure washers can force water into the bearings. You can use car shampoo but not washing up liquid, though plain water is good too.
WAsh the bike with the brush and wipe it dry.
If you want you can take the wheels off and using a rag clean the rims etc. Car shops sell degreaser and you can spray that on the chain to clean it (be careful not to spray it near the pedals or gears). Use a toothbrush or scrubbing brush to clean in between the links. It is better to take the chain off using a chain splitter and soak it in degreaser, then use a brush to get rid of the gunk.
Use a rage to wipe the gears when the chain is off.
It depends how much time you have to clean the bake with but you can clean the bike well.
After it is shiny and clean and if needed the chain put back on again, then you have to oil it again. You can use a spray oil like WD40, on the chain but be aware that this doesn't last long - you have to oil the chain every other ride or something, every ride if you go off road and through water. Engine oil is thicker and is a bit better or a propriety chain lube can help.
Obviously after oiling make sure that there is non on the rims and brake pads (if there is then degreaser onto a rag and wipe off), and wipe off any that is on the frame as well. Basically after cleaning oil on anything that moves.
