For Ruler of the 6th traveling to and residing in another house–Think “Service, Service, Service”.
Ruler of the 6th in the 6th—The 6th House will be a Theme for the native. The 6th House rules service and health, as I said. The native may put stress in to his body. The native may have health issues. One would need an experienced Astrologer to check this out.
R of the 6th in the 7th—the native will serve his partner
R of the 6th in the 8th–the native will serve using taboo subjects such as a sex educator
R of the 6th in the 9th–the native will serve using intellectual ideas such as a professor
R of the 6th in the 10th—the native will use his career for service. This could be an honest politician
R of the 6th in the 11th–the native will serve in groups
When we go in the other direction, it is harder. However, it gets easier with doing.
When ANOTHER House puts its House Ruler in to the 6th, think Using that House as his TOOL to serve. That House will be his HAMMER. I will give some examples.
R of the 11th in the 6th–the native will USE his role in the group as his TOOL to serve. This may be a Spokesman for a group such as Green Peace.
R of the 10th in the 6th–the native will use the TOOLS of the House to serve. This may be a successful businessman who mentors up and coming small businessmen.
R of the 9th in the 6th–the native will use the TOOLS of the House to serve. This may be a professor who really cares about his students. It may be an Astrologer with a passion to help. I think of Howard Sasportas, as he is my favorite.
R of the 8th in the 6th–the native will use the TOOLS of the House to serve. This may be a sex educator or a detective. This may be an FBI Profiler, which would be the quintessential example.