how to handle multiple part appraisers in OSA

how do I configure the system for two part-appraisers and one final appraiser?

1. do I need to configure two standard columns PAPP?

2. how do I autorize partappr1 to access PAPP column 1 and partappr2 to access PAPP column2?

3. how to specify who the part appraisers are? ex. john doe is partappr1 and mary jones is partappr2.

4. do I need two process steps in the process flow (step1="partappr1 feedback completed", step2="partappr2 feedback completed" )

Thanks,

Tiberiu