It was reported in some narrations that Imam Mosa Al-Kadhim â€“ our Seventh Imam (peace be upon him) â€“ said to his one of companions: â€œIf you have a request from Allah say: Allahumma inni Asâ€™aloka bi haqqi Mohammadin wa Alliyyin fa inna lehuma shaanan minash-shaan, wa qadran minal-qader, fa bihaqqi dhalikash-shaan wa bihaqqi thalikal-qader, an tosalli alla Mohammadin wa Aal-Mohammad wa anâ€¦â€¦." then you mention your request.
The translation of the said supplication is: O my Lord I ask you by the right of Mohammad and Ali as they have a (high) position amongst the positions and a (high) value amongst the values. By this position and this value praise be on Mohammad and his progeny andâ€¦â€ then say what your request is.
There are other supplications mentioned in books of supplication.
It is not permissible to shave the beard unless growing it causes harm and hardship. If it causes tolerable discomfort then it must not be shaven. The itchiness that you feel is probably because you are not used to growing it.