Here's a tip (?) for detergent cleaning of E61 groupheads. The normal procedure is to put about 1/2 teaspoon of your chosen favorite (Joe-Glo, Cafiza, etc.) into a blind filter basket and run several backflush routines. The exact instructions and recommended frequency are on each container.
One of the drawbacks to this procedure is the removal of coffee oils from the surfaces of the cam and pins which control the brew and preinfusion/exhaust process. You should notice a little squeaky-squeaky noise with movement of the brew lever until the appropriate surfaces get recoated with coffee oils. Excessive detergent cleaning will lead to premature wear of both the cam profile and pin surfaces - about a $50 fix.
A way to avoid this is to perform the backflush routine as usual but instead of moving the lever to the exhaust position, simply shut the machine off with the main power switch and with the lever remaining in the brew position. Let the machine rest and parts soak for 15-20 minutes and then turn the main power switch on again for 5-10 seconds and then off again for another soak period. Follow all this with a lengthy flush of the grouphead.