Ask an Alim

Waalykum salam
Thank you for your question

So what you are doing is already highly recommended to do.
All I can add is the following that is narrated by Imam al-Ridha (s) that one should place his hand on the grave and recite surah Qadr 7 times. Surah Mulk n waqeah are recommended too.

Also, it highly recommended to pray for the deceased while sitting towards Qibla.

Another dua that is recommended to recite is as follows:
1) «اَلسَّلامُ عَلى اَهْلِ الدِّیارِ مِنَ الْمُؤْمِنینَ وَالْمُسْلِمینَ، اَنْتُمْ لَنا فَرَطٌ، وَنَحْنُ اِن شآءَ اللهُ بِکُمْ لاحِقُونَ»

2) «بِسْمِ اللهِ الرَّحْمنِ الرَّحیمِ، اَلسَّلامُ عَلى اَهْلِ لا اِلـهَ اِلاَّ اللهُ، مِنْ اَهْلِ لا اِلـهَ اِلاَّ اللهُ، یا اَهْلَ لا اِلـهَ اِلاَّ اللهُ، بِحَقِّ لا اِلـهَ اِلاَّ اللهُ، کَیْفَ وَجَدْتُمْ قَوْلَ لا اِلـهَ اِلاَّ اللهُ، مِنْ لا اِلـهَ اِلاَّ اللهُ، یا لا اِلـهَ اِلاَّ اللهُ، بِحَقِّ لا اِلـهَ اِلاَّ اللهُ، اِغْفِرْ لِمَنْ قالَ لا اِلـهَ اِلاَّ اللهُ، وَاحْشُرْنا فى زُمْرَةِ مَنْ قالَ لا اِلـهَ اِلاَّ اللهُ، مُحَمَّدٌ رَسُولُ اللهِ، عَلِىٌّ وَلِىُّ اللهِ.» this dua is By Imam Ali (s), which is recommended to be recited upon entering the grave yard

Hope this helps
N.S.Jaffery