Hi,

In our laboratory, we usually use goat serum and BSA at the same time as a blocking solution for 1 h at room temperature. This step allows to significantly reduce the chance of having non specific antibody binding. You don't necessarily need a second source of protein in the subsequent steps. The formula is as follows for the blocking reagent: 5% BSA/10% goat serum/0.05% sodium azide in PBS 1X. For primary and secondary antibodies, we dilute them in 5%BSA/0.05%sodium azide in PBS1X. The concentration of the primary antibodies depends on the manufacturer. I would suggest looking at the company's data sheet for this information.

Here's a paper from my colleagues laboratory on the method. Feel free to ask more questions if needed.

Article Production, Titration and Imaging of Zika Virus in Mammalian Cells

there is no order, you need to make a solution in 1%PBST first. Take 95ml 1%PBST, add 2g BSA, add 2ml NGS, Leave for 45 minutes at room Temp, BSA take time to dissolve. If needed, small sterile magnet can be used to dissolve but is not essential. After that add 1% PBST to make to 100 ml volume, filter with 0.45um or 50um filter to remove undissolved particles. Use this solution to dilute your antibody

Either one alone should be fine. (In fact we use FBS.) Your best bet is to test them alone and together and compare the results.