"You (Muhammad sal Allahu alayhi wasallam) are the one, with whom Adam made Tawassul and even he was your father, he was rescued. When the Khalil made Dua to you, the fire became cool against your bright Noor the fire was calmed. Prophet Ayyub (a.s.)made Dua to you, when he was sick all his sickness was deleted, when he made Dua to you!" So is Musa making all the time Tawassul with you on the day of judgement he will search help by you!" (Bayt 9-13) "Make Shafaat for this poor ya Rasulullah Madat! I did came to your door, begging for richness by you!" (Bayt 49)
Thirdly, (Abu Hanifa An Nafi An Ibn Umar): The appropriate way is that you turn towards the grave of Prophet (salallaho alaihi wasalam) coming from the qibla while HAVING YOUR BACK TOWARDS QIBLA, FACING DIRECTLY TOWARDS THE QABR AND SAY PEACE BE UPON YOU [Ya Rasool Allah] O PROPHET OF ALLAH AND HIS RAHMAH AND BARAKAH. [Musnad Imam Abu Hanifa, Bab Ziyarah Qabr an Nabi Sal Aallahu alaihi wasallam]
Fourthly, Mujtahid, Imam ibn al-Humam (d. 861 AH), mentioned from Imam Abu Hanifa in his Fath al-Qadir (Sharh al-Hidaya) the following narration:
“When Imam Abu Hanifa visited Medina, he stood in front of the honorable grave (of the Prophet) and said:
"O (YA), most honourable of the Two Weighty Ones (humankind and jinn)! O (YA), treasure of mankind, shower your generosity upon me and please me with your pleasure. I am aspiring for your generosity, and there is no one for Abu Hanifa in the world but you."
Next, coming to Imam Shafi’i, Imam Ibn Hajar al-Haytami said in his book al-Khayrat al-hisan fi manaqib al-imam Abi Hanifa al-Nu`man, chapter 35: When Imam al-Shafi`i was in Baghdad, he would visit the grave of Imam Abu Hanifa, give him salam, and then ask Allah for the fulfillment of his need through his means (yatawassal ilallah ta`ala bihi fi qada' hajatihi).
Imam Kawthari mentioned in his Maqalat (p. 412) that the hafiz al-Khatib al-Baghdadi mentions Shafi`i's tawassul through Abu Hanifa in the beginning of his Tarikh Baghdad (1:123) with a good chain.
Haytami also said in many places in his book al-Sawa`iq al-muhriqa li ahl al-dalal wa al-zandaqa (cf. p. 180) and al-Khayrat al-hisan (p. 69): "Imam Shafi`i made tawassul through the Family of the Prophet (Ahl al-Bayt) when he said: Al al-nabi dhari`ati wa hum ilayhi wasilati arju bihim u`ta ghadan bi yadi al-yamini sahifati [The Family of the Prophet are my means and my intermediary to him. Through them I hope to be given my record with the right hand tomorrow]. This is found in Diwan al-Shafi`i as edited by `Umar Faruq al-Dabbagh (Beirut: Dar al-arqam, n.d.) p. 50.
How could you turn your face away from him when he is the means (wasila) of your and your father Adam's forgiveness to Allah on the Day of Resurrection? Nay, face him and ask for his intercession (istashfi` bihi) so that Allah will grant it to you as He said: "If they had only, when they were wronging themselves, come unto thee and asked Allah's forgiveness, and the Messenger had asked forgiveness for them, they would have found Allah indeed Oft-returning, Most Merciful (4:64)."
It is cited by al-Qadi `Iyad in al-Shifa (2:92-93) with a sound (sahih) chain, and also cited by Samhudi in Khulasat al-Wafa, Subki in Shifa' al-siqam, Qastallani in al-Mawahib al-laduniyya, Ibn Jama`a in Hidayat al-salik, and Haytami in al-Jawhar al-munazzam and Tuhfat al-zuwwar. See also Ibn `Abd al-Hadi in al-Sarim al-munki p. 244. Ibn Jama`a says in Hidayat al-salik (3:1381): "It is related by the two hafiz Ibn Bashkuwal and al-Qadi `Iyad in al-Shifa' after him, and no attention is paid to the words of those who, based on their idle desires, claim that it is forged.
“And in this hadith is proof for the permissibility of tawassul through the Prophet [sal Allahu alayhi wasallam] to Allah (swt), with the conviction that the [actual] doer is Allah (swt), and that He is the Giver and the Withholder. What He wills is, and what He does not will, will never be.”