I have read that there is no importance to Qul/Khatam or Barsi, but people do it. When someone do Qul of a deceased one, what should one recite? I don't know Arabic Quran so what else can I do? And if someone visit deceased grave. What dua should one read?
If you visit deceased grave, you can read any portion of Quran (fatihah, small surah, etc.) with the intention of sending the rewards to the dead person.
There are no precise time or day to do this, you can do it whenever you want... You can also do it from home.