I've never had an issue with the comfort access. The trunk is a bit iffy, but I can usually get it working pretty easily now.
The unlock sensor should unlock as soon as you touch it - it's on the inside of the handle. The strips/ridges on the top of the handle are where you press to lock it, make sure you aren't touching both.
Out of curiosity do you have very dry skin? I have no issues with the sensors even with gloves on, but technologically speaking some people, especially older people with dry skin are prone to having more issues. My mother has a oven with capacitive controls and literally can't use it in winter. She'll push and prod the buttons with all her might and her fingers just don't have the "juice" to trigger the sensor, and I've never had an issue.
Try to make sure you're only touching the inside area and to make sure the key is close enough. Perhaps try to take the key out of your pocket and see if it lets you open it easier - it's possible something is causing interference so that your hand isn't the problem it's the key. (Though my wife leaves her key in the purse and it never has an issue)
Current: '15 M235i Vert
Previous: '13 335i, '08 TL-S, '00 Corvette