Answer
(Fatwa: 1512/1512/M=1431)
You should recite لا حول ولا قوة الا بالله seven times after reciting ta’awwuz (اعوذ بالله) and tas’miyah (بسم الله), and blow on water and give it to your wife to drink, or let your wife know this practice so that she could do it herself.
Fatawa Rahimiyah deals with the method of intercourse in detail; also, you can study other books like “Poshida Raz” and “Tanhai Ka Sabaq”.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband