How do you manage big projects (hundreds of files) using only VIM?
I personally start having problems in any larger than small project.
VIM has excellent support for tags. Once you have created a tags file for your project, you can jump to a definition or declaration of a method, class, etc., including jumping across files, all inside the same editing session.
Try
:help tags
To generate a tags file for C/C++, go to your shell prompt (I'm assuming your system is *nix/Cygwin) and type
info ctags
or
ctags --help