I learned from an older tech when i started. Gas trucks are a given that you will have to spray out the distributor cap with contact cleaner. Ensure that you don't directly spray the dash area (ECM's etc are normally mounted there). Blow dry well. The cleaner truck runs better and it's easier to find those little seeps and leaks that seem to exist on the older units as they age.
Electric trucks are different.
There are a couple of wasy I've seen. i prefer the 'safest'. Unplug battery and remove (to clean under). Wash the heck out of it (it'll get the mud out), blow down and then park for three days to drip dry before you even think of plugging in a card. I've seen of rebuild shop pull all cards before washing to ensure that there are no issues..