Raytof.... is exactly correct. My personal technique was to open the dumps, and then close them if I had to take my hand off the switches! Just too easy to be distracted until the 'Amber' fuel light+Cross Feed etc.....
I know of one pilot who was distracted by a glove on the coming!! whilst wondering how it got there, and why was his hand cold... the lights started flashing..... you guessed it: Amber Fuel+Cross Feed etc...... Doh! Got back, but lucky for him the taxi in was short!
Advo