I think you can use the expression with mí with any month, but it changes the name of the month to the genitive case. (Sometimes the two forms are the same.)
You don't need Mí in front of Feabhra. I believe that you need Mí only in the names of November (Mí na Samhna or Month of Samhain) and December (Mí na Nollag or Month of Christmas) because those two derive their names from holidays.
Go ndéana sé maith duit!
Also, and I hope this doesn't sound too pedantic, when you address someone, you use a special form (the vocative case)--basically, you lenite the first consonant if possible and. if it's a masculine name, you make the last consonant slender if possible. When you write it, you use the particle a:
a Cháit, a Pheig, a Mháire
a Shéamais, a Sheosaimh, a Mhaidhc
When you speak, that little a is kind of ignored because there's no stress on it.
Go n-éirí go geal leat!