As an amateour actor i take parts in comedy productions and every time i use my voice to make people laugh.Usually what i do is exaggerating the accent in a funny way together with changing my voice to make it sound funny.
In a play called BOEING BOEING i was given a role of a guy who was arranging girls for the main character. I made my voice to sound like a geezer like those guys in Only Fools and Horses which is funny london accent. Another time i was given a role of a Black Sea Region Turkish character which i have made exactly the same accent as a native turkish that many people thought i was accually from there.
I don't have any official training or anything.All i did is using my voice in plays.
I can do many of the accents or voices which needs to be imitated. Of course i have some limits, but all i need is to keep listening to learn how to do it if i can not do it at all.