Hmm, no wonder you prefer CtrlP to your previous workflow, find and grep are two horrible and verbose tools for opening files from Vim!
The canonical way to open a file for editing is:
:e file
Of course you can use tab-completion:
:e fi<Tab>
And the "star" wildcard:
:e f*/fil<Tab>
And the awesome "starstar" wildcard:
:e **/f*/fil<Tab
It's even better if you activate the "wildmenu" and play with the "wildmode" option:
filea fileb filec filed
------------------------------------
[filea] fileb filec filed
------------------------------------
:e filea
CtrlP is a great plugin that I use extensively all day long but… there are other ways, beyond find and grep.
