It's not much complicated. I have been to Saudi & Bahrain during recent holidays. Procedures are as follows:

1. Apply for Bahrain Visa at the Bahrain Embassy. Contact them on phone and they will fax u the application form. A 3-day visa will cost you QR 150 per passport. Original NOC addressed to Bahrain embassy + copy of Immigration Card of the sponsor is required with the application. This is for signature verification. You can have the visa on the same day. Once stamped, entry period is 1-month.

2. After getting Bahrain visa, contact visa processing agents for Saudi Embassy. You cannot approach Saudi embassy directly. Again NOC is from sponsor is required. If car is rented, NOC from car rental company is required. You can have the visa within 3-working days without any hassles. Visa cost is QR 125 per passport including agent's fee. It is a two-way visa enabling you to travel to Bahrain thru Saudi and return. You can stay in saudi 3-days while going and 3-days while returning. Once the visa is stamped, entry period is 1-month.

Search QL site to get contact details of agents for saudi visa process.