You do NOT clean a thermocouple.
They are really inexpensive and when they are giving problems have a LMP / or Gas fitter replace it
Spillage , bad thermocouple
Fill with water, maintain 2-3 days, stir, empty the tank; wash again with hot water.
There are many pictures of this on Google.
$6 to $10 depending on where you are and where you get it from.
Shut off the gas let the tank cool THEN get a soft cleaning agent such as soft scrub or Fantastic , clean soft cloth and carefully clean the out side of the tank
You shouldn't need to clean the pilot. If it frequently goes out you need anew thermocouple.
I make plenty of room to stretch out, shut the gas valve. Remove the entire burner assembly remove the defective thermocouple clean the burners, install the new thermocouple and reinstall the thermo couple and turn on the gas and test all the connections for leaks. If a leak should go undetected there is a very good chance of causing an explosion
THERMOCOUPLE or defective gas valve
The hot water tank might be undersized for your usage.
do they help with hot water tank replacement
how long does it take for hot water after lighting water tank its gas?
You light the pilot. if it will not stay lit,the thermocouple is bad.