Help needed with arranger.ly

[Eef Weenink]

I need some help to get this nice program really running. 

I read the manual several times,studied NOTES.ly etcetera and now able to get the first parts of music on the correct place. :-) 

(I am using a score with 6 instruments and I am trying to arrange this or other combination of instruments. If needed I can give an example, but that is a lot of work, so hopefully my description is enough. )

Question1: 

- How to insert a clef change at a specific point? 

I have two voices in lefthand of piano, created like: 

  (rm 'leftOne  1 'leftOOne '(8 16)  )

          (rm 'leftTwo  1 'leftOTwo '(8 16)  )

Now I need a clef change in bar 7, to change clef from treble to bass. 

Question 2: 

Having two voices in left hand, I want to insert the command to get stems of both voices in same direction. So in both voices I need to insert: 

 \stemDown 

I have no idea how to do this. 

Probably same questions for inserting articulations, slurs, etcera, 

Normally I would do that in the source of music, but when arranging that is not the way to go, because I want to reuse the same material perhaps with other slurs/etcetera. 

Maybe it is in the manual, but I did not find it. 

regards, Eef Weenink