Asalamualaikum, InshAllah I hope you are well.
My question for you is?
Is it permissible to go to the grave of a deceased pious person i.e Darbars etc and make Dua Fatiha and then in another Dua use the Wasila of that pious person to ask Allah 
in accepting the Dua made? In the second dua the person asks for something ie. Rizq, health, Children. The person is asking from Allah but only using the Pious persons Wasliah.
JazaAllah
Answer:
In the name of Allah, the most Beneficent, the most Merciful.
According to the majority of the scholars it is permissible to visit the graves of pious predecessors and scholars.
Allahmah Ibn Abeedeen Shami 
uses the hadith of Musanaf Ibn Abi Shaibah , that “the Prophet of Allah 
used to visit the graves of the Martyrs of Uhud every year” to prove one is allowed to visit the graves of the pious predecessors.
Even though some immoral and cultural practices take place at such graves, which are against the teachings of Islam, this should not prevent one from visiting the graves of the pious predecessors. (Raddul Muhtar P.150 V.3 & Darse Tirmizi P.115 V.2)
With regards to praying near the grave, as a rule in general, to lift the hands during supplication is mustahab and therefore this also applies when supplicating at the graveside. This is supported by the narration of Ibn Masood 
which has been mentioned by Hafiz Ibn Hajar in his book Fathul Bari a hadith that, “I saw the Prophet by the graveside of Zun Najadain … and when he finished the burial he turned towards the qibla raising both hands.” (Fathul Bari, Vol 11, P173)
In another place Hafiz Ibn Hajar records a narration of Aisha 
in regards to the Prophet’s supplication for the dwellers of Baqi “He raised his hands thrice.” (Fathul Bari, Vol 11, P171)
Finally, the Allah states in the Quran: “O you who believe! Fear Allah and seek a means (wasila) to be closer to him…” (Surah Maida: 35)
In another ayah Allah states: “…If they would have come to you when they had wronged themselves to seek Allah’s forgiveness and if the Rasool had also asked Allah’s forgiveness for them, they would have found Allah Forgiving, Merciful.. (Surah Nisa: 64)
It is clear from the above verses that tawassul is permissible and there is no difference between the living and the dead in this matter. However there is difference of opinion of the scholars in the tawassul mentioned above in your question. This difference stems from the fact that do the dead hear the living.
Sayyiduna Maalik al-Daar, the treasurer of food during the time of Sayyiduna Umar ibn al-Khattaab [radhiallaahu anhu], reports that once the people had been experiencing a drought in the era of Sayyiduna Umar [radhiallaahu anhu], a man went to the grave of Rasulullah and said, ‘O Rasulullah , ask for rain on behalf of your Ummah, for verily, they are being destroyed.’ Thereafter this person was instructed in a dream to go to Sayyiduna Umar and tell him that, ‘the rains will soon come and say to him, be intelligent’, When Umar was informed of this, he began to cry and he said, ‘O My Lord, I will only leave out what I am unable to do.’ (Musannaf ibn Abi Shaybah p.31-p.32 v.12; Dalaailun-Nubuwwah of Imaam Baihaqip.47 v.7).
The conclusion we can come to is that it is permissible to visit the graves of the pious predecessors as long as no innovations and shirk goes on. Furthermore, it is permissible to do tawasul as long as one is asking Allah through the blessings of these great scholars and pious people.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.