1. Explain it simply
Doubling a measure word (个个/天天/件件) means 'every single one'.
It stresses that a feature is shared by all members of a group.
Put 都 right before the predicate: (Noun) + MW-MW + 都 + predicate.
2. Show examples
同学们个个都很高兴。
Tóngxuémen gègè dōu hěn gāoxìng.
The classmates are every one happy.
个个 = each one
这些衣服件件都很漂亮。
Zhèxiē yīfu jiànjiàn dōu hěn piàoliang.
These clothes are every one pretty.
件件
这个星期天天都吃羊肉。
Zhège xīngqī tiāntiān dōu chī yángròu.
This week I eat mutton every single day.
天天
3. Share a tip
Doubling a measure word (个个/天天/件件) means 'every single one' and almost always takes 都 before the verb.