I spend the first 12 years of my professional career doing make up effects. The difference between 30's and 60's is very subtle - some weight gain (thus the prosthetics), very slight drooping of the skin around the neck and eyes, skin tone is a bit blander with some wrinkling around the eyes and mouth.
My personal opinion is a website isn't going to be able to teach you this very complicated, exacting process. However, if you cannot get in touch with a makeup artist then type "make up effects" into Google and you'll find hundreds of sites dedicated to this craft.
It took me two or three years of experimenting to be able to age actors convincingly for film. And even then I never got it to look right. Extreme aging like Dustin Hoffman in "Little Big Man" is much easier than the subtle aging from 30's to 60's.
You're attempting one of the most difficult processes in make up. My suggestion is if it's important to the story that the audience believes it, you should hire a makeup artist. A good one isn't cheap - but your final movie shouldn't look cheap either.
Good luck. You'll have fun learning about makeup effects.