I always found it interesting that Rutherford did not participate in the required ministry. His excuse was he was too busy running Watchtower business. Do as I say and not as I do. - Rutherford
Rutherford is no different to most higher-ups in the Org. It's actually quite surprising how little ( if any ) actual door knocking is done by the prominent ones in the Society. Ray Franz mentions in his books that most of the GB and other higher-ups did very little actual ministry.
I worked in London Bethel for a while and was struck by how little ministry was actually done by anyone - they were supposed to go out on Sunday but very few bothered ( in fairness , most of them were pretty depressed and knackered - back then it was 5 1/2 long days a week , getting up at 6am - much of the work very boring and mundane ( such as cleaning or working in the printing press or laundry ).
Where I lived there was a house where Bethelites used to stay almost every week on vacation ( a JW living abroad had it as a holiday home & allowed free accommodation for Bethelites ) and they very , very rarely even did a token hour of ministry all week ( or 2 weeks ) they were there. Many times they didn't even turn up at a single meeting even though the Kingdom Hall was five minutes drive away ( my wife was a keyholder and we would often clean the house so we knew when people were staying ).