Do "lipstick on a pig" and "画蛇添足" share the same meaning?
画蛇添足 means 'ruin things by adding unnecessary, inappropriate addition' 

Adding legs on a snake in a painting not only doesn't improve its quality , it actually ruins it by adding unnecessary, inappropriate addition 

For example: 

Man: "I love you"

Woman: "I love you too"

So far so good

Man: "I love you as much as I love my dog"

Now it is too much information, the second sentence from the man is '蛇足'(unnecessary, inappropriate addition)

"lipstick on a pig" means something entirely different. It means " wasted effort", a pig is a pig, no matter how much make up you put on it, it can never looked like a pretty lady.