Your toddler is 31 months old!
This month your toddler may be able to perform simple tasks such as brush his teeth by himself and comb his hair (although you will need to go over both tasks again just to make sure they are done properly). Although his growing independence means he wants to perform every task on his own, this will probably result in frustration over the tasks he cannot deal with.
Don’t be surprised if when helping him to get dressed, discovering he can’t manage the buttons results in a mini tantrum from him. He badly wants to be independent, (and you badly want to help him) so you both need to find a middle ground – why not suggest he tries the first two buttons and if he can do those he can do a third before you come and help.
Distraction is a great method for calming a tantrum. Why don't you try baking with your toddler.