Arguments and URL strings

Hi,

maybe this is a really silly thing, but I´ve trying to figure out how to accomplish this for a couple of days with no results.
I want a section in my site to have different subsections of the form

/main-section // it displays last content submitted for each sub-section. For each subsection the URL will be:

/main-section/subsection-x // and it contains a teaser of nodes for each subsection-X (x=1,2,3...). Finally I want the full view node to have the URL:

/main-section/subsection-x/node

Well, and this is my approach on how to implement it:
1) Create a panel with the following URL arguments as path: /%main/!sections/!node
2) Then, I assign a context for each argument which is a String in all of the cases. The option "Get all the arguments after this one" is active in each case, except in the first argument "%main".
3) Create a variant for each argument and set a Selection Rule for each one that contains the URL section to be activated in each case. For instance: in order to get activated the variant for "subsection-1" I choose a Selection Rule that has a URL string "subsection-1".
4) Results: Page not found.

I guess I´m missing something important about how arguments and contexts work in Panels. I´d like to find documentation for a better understanding of this but I didn´t found anything clear at the moment. Could you suggest some and/or point out what is wrong in the implementation proposed?

Thanks!