Bio burden reduction

I am looking for a procedure to reduce bioburden when filling.

We have a 0.22 µ filter betweeen the bulk and the buffer vessel on the filling line. We want to install small one time use filters on each filling needle.

My questions are:
when do you do the bubble point test of the big .22 filter (between bulk and buffer vessel). Only when the batch is finished or also before…
If both before and after , how do you assure the filter is not damaged when you install it in the process?

What kind (brand and type) of filters can you use to put on the needles… preferably small triclamp coupling…

Thanks for any feedback