The most eminent Deobandi scholar, known as “Hakim-ul-Ummat” - Ashraf Ali Thanwi (1863-1943) wrote that it is both permissible and possible to acquire assistance from the dead in their graves!
Writing on the subject of
قبروں سے مدد چاہنا
Ashraf Thanwi comments:
ہاں! ان سے وہ چیزیں مانگو جو ان کے پاس ہوں تو اب بھی صاحب نسبت ان سے فیض حاصل کرسکتا ہے
Translation: “Yes! Ask them (inmates of the graves) for that which they actually possess, for even now the Sahib-e-Nisbat [person connected through Sufism, mysticism, etc.] can acquire blessings and benefits from them.”
Reference: Ashraf ul Jawab, p.113