How can I get our graphic designer up to speed on grids?

We would like to use a grid system (960.gs) for our new designs, but no one on our team has used them. We also have at least one design done without it being designed around a grid. My questions are:

How fast can a graphic designer learn to design for a grid?

Can designs be retrofitted for a grid?

About 2-3 minutes

Most designs could be shoehorned into a grid system in some way unless they were freeform fluffy dumplings.

Designing to a grid is a very logical way to do things and keeps it tidy, regulated and ordered. Any designer worth their salt should either know already or be able to adapt to grids pretty damn quickly