Walaykumusalaam warahmatullahi wabarakaatuh,
What you are asking about is referred to as istighātha, a style of supplication to Allah (subḥanahu wa taʿala). Both istighātha and tabarruk are, in fact, a form of seeking the means (ar:tawassul).
Allah (subḥanahu wa taʿala) says:
"O you who have believed, fear Allah and seek the means [of approaching] Him." [5:35]
The erudite scholar and shafiʿi jurist , sayyid Alawi al-Jufri (d.1273H) said:
"When a person says, in a situation of need, " Ya Fulan!," he is seeking the person being called as a means to ask Allah (subḥanahu wa taʿala) for help, and the fact that he calls out to the person and not Allah is what is known in Arabic as majāz (metaphor). The meaning of the Arabic term 'Ya Fulan! [Help me]' is:
"O so-and-so, I seek you as a means to ask my Lord to help me."
Therefore, the one being asked in reality (ar:ḥaqīqa) is Allah (taʿala) and the use of a prophet or a righteous person is metaphorical."
Imam Shihāb-ud-dīn al-Ramli said:
"istighātha through the prophets, messengers, awliyāʾ, and righteous scholars is permissible because the miracles (ar:muʿjiza) of the prophets and the miracles (ar:karāma) of the awliyāʾ do not cease with their death."
The mufti of the ṣhafiʿis in Makka, Ahmad Zaini Daḥlān said:
"The upshot is that the madhhab of ahlu-s-sunna wa-l jamāʿa is the permissibility of tawassul and istighātha with the living as well as the deceased, because we do not believe in any effect, benefit, or harm except through Allah alone, without any partners. The prophets cannot effect anything, rather the blessing is sought through them and istighātha is done through their rank because they are beloved to Allah (taʿala). Those who differentiate between the living and the deceased are the ones who believe that the living can effect things while the dead cannot, but we say that Allah is the creator of everything, "Allah created you and that which you do."
The objective of tawassul and istighātha being only to get blessings by mentioning the names of beloved servants of Allah for whose sake Allah may grant mercy to creation, be they living or dead. The actual author of existence is Allah alone, they are only customary causes, they produce no effect on their own."
Allah knows best.
Bughyat al-Mustarshidīn, Abdur-Raḥmān al-Mashhūr (Dar al-Faqīh, v4,p483)
Fatawa al-Ramli, Shihāb-ud-dīn al-Ramli (al-Maktaba al-Islamiyya, v4,p382)
Khulāsat al-Kalām, Ahmad Zaini Daḥlān