Yep – ram will help.
External drives won’t help though – usb works, but it’s not great. Internal works off a much faster bus, so you’ll want to add another internal drive if you’re able.
A graphic card with dedicated onboard video ram will help too.
That said, 4 years is a long time to push a machine used for graphics. I’m having to bite the bullet myself – pushed my machine just over 3 years, and now I’ve a new box on order.
It’s just a fact man – these suckers do become dated.
Good luck.