I carry a Glock at work and had trouble with the slide release using my trigger finger. Some righties had trouble with it as well as it pushes into the slide slightly if it is pushed in instead of straight down.
You can add an enlarged slide release, which is far superior in every aspect regardless of which hand you use. There are also at least 3 different magazine releases available, each one thicker and thus projecting further from the grip allowing easier engagement with the middle finger of the left hand or the index finger of the right hand.
I hope this helps, it sux being a left handed shooter but I love watching righties fumble around when firing weak handed while we finally get to shoot without having to fight using our weak hand and the engineering of the gun.