If the owner is busy or not willng to come with you, you can get him to any near nadra e-sahulat service centre. You can find about these centres from google. Get that RTO biometric slip. takes around less than i minute to do bio-metric and cost around 300 to 500Rs.
If he has smart card, then smart card, NIC copy of the previous owner and new owner, transfer letter validity of one month if date is mentioned, RTO slip valid for 2 months, Go to Islamabad excise website download and print relevant documents for transferring the car. Check for any online transferring of the car.
If the car is paid lifetime token tax then its ok. if not then you have to pay lifetime token tax before transfer the car, otherwie they wont transfer it. if the previous owner is filer person then you have to pay 21000 token tax and if he is non filer person then 31000. and i guess 2,3 thousand for all process fee etc.
When you will be done with the process, please do share with us your experience because "kab konsa koi new rule etc ajae pata b nahi chalta
".
Goodluck!!