if you use vim add the following to your .vimrc

set formatoptions=r
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after your initial # comment goes here - each time you hit a newline, a # will be placed at the beginning... or/and to .vimrc

" comment out blocks 
" ma to mark beginning
" put cursor at the end and hit F7
" code will be commented out
map <F7> :'a,.s/^/#/gi^M:nohl^M
map <F10> :'a,.s/^#//gi^M:nohl^M
[download]

I believe I got that last one from a thread here...