I know exactly how you feel, I have arthritis in my hands. The type Harness' I use (see link) are easier than most. Putting them on is quite easy, and the disconnect is the problem. I'd rather have it that way, at least they're installed properly, rather than missing getting a buckle securely snapped.
http://www.petsmart.com/supplies-training/harnesses/grreat-choice-dog-harness-zid36-8827/cat-36-catid-100082?_t=pfm%3Dsearch
Fitting/adjustment Tip:
Snug with the body/chest strap, relaxed with the shoulder straps.