TA/RA experience and recommender tracking

[cloudyword]

Hi folks,

I've had both TA and RA experience for 2-3 years during undergrats (because back then, our department did not have grad programs yet). This experience was half bliss and nightmare for me because of all the hard work and challenge it required. My questions are: 

1) How do I subtly mention my TA/RA experience as a bonus in my SOP, even though this is not exactly the same as how RA/TA system works in the U.S.? (I did not have to teach classes, only led in-class discussion at times.) Would it strengthen my candidacy for Ph.D entry directly from BA?  

2) Is it necessary that I secure my professor/boss whom I worked for as one of my recommenders, and make sure that s/he writes about my TA/RA experience? Would it worth the risk when s/he is not that reliable/willing/available?   

Any comment would be appreciated!