I applied for an internship quite a while ago (2000) and a job (2002) so things might have changed. However, we were given an aptitude test and those that passed were given two interviews (I dropped out after the first because I got offered a placement in Switzerland for the internship, I had decided to do a PhD before I got to the interview stage in 2002), however one was a technical interview (R&D) so I'm not sure if that this really applicable for marketing.
I'm guessing that they do an initial cull based on CVs and application forms then they do the aptitude test and then they interview.
Actually, I've just looked on P&G's website and that is exactly the format of the procedure. I strongly suggest you look at the website if you haven't already.