How to customize bootstrap theme non-destructively?

[johnywhy]

hi

i'm using theme "Spectral", which is based on bootstrap. 

i want to override some css with my own css, 
but i do not want to alter the theme files. 

i tried some simple css changes to the themes css, and did not get same results as when applying same changes to my browser's developer pane. i'm guessing this has something to do with bootstrap's responsive css. 

is there a recommended way to do this?
i've read a bit about kickstrap-- is that a good solution?
how to install on GS?

the bootstrap "customize" page says simply:

The web customizer is no longer available for outdated versions of Bootstrap.

which does not make sense, since that page is linked on bootstrap's homepage. 
http://getbootstrap.com/2.3.2/customize.html

thx