You can drop all your applications to both Hong Kong and mainland China to Consulate-General of the People's Republic of China in Jeddah. The requirements are as follows:
1. Actual passport of more than six months validity with a blank visa page.
2. One complete application form (The People's Republic of China Visa Application Form) with one recent passport size photograph (black and white or color).
3. A tourist visa invitation from a Chinese tour agency or an invitation letter from relatives to be visited.
4. Additionally, you may be required to provide personal bank statement and actual airline tickets showing departure from China.
5. Your residence permit in Saudi Arabia and its copy.
As your plan, you need a double entry visa to Hong Kong. For applying a Hong Kong Visa, the applicant has to submit the following papers:
1. The invitation letter from any Hong Kong company or local government. A clear faxed paper is acceptable.
2. The company sponsor letter notarized by the local Chamber of Commerce.
3. Personal account or sponsor's account (e.g. company) statement issued by any commercial bank.
4. Copy of the passport, iqama and exit & re-entry visa.
5. Fill the HK application form affixed with one photo on it.
Every paper mentioned above should be in English.