and second question, why not green address? is it a good choice too?
2. No idea about Green Address... I've not used it.
The main reason for suggesting Electrum is that:
a. I know it works (personally tested it)
b. there are the n00b friendly video tutorials (that mean I don't have to explain how to do it!
![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)
c. In the case of MultiBit HD, Electrum is one of the few wallets that works with the Derivation Path m/0' (most wallets don't use this and/or don't allow you to specify it)