Lots of nice information in sol's post, I can't add much more to that - the way I tend to end my block string is either with a 3C or a 2C. 2C for the +1 frame advantage and 3C since its jump cancel-able.
My block strings could go like this:
dash 5B, 5C, 2C...
dash 5B, 5C, 2C,3C(JC)...
dash 5B, 2B,3C(JC)...
in the corner:
5B,2B,6B
5B,2B,3C
You can use this is a starting point then when you get more confident, start messing around with Rcing and the like.