Also, which needles are you using and can you provide a link to where your purchased them.
For injection, I used very thin yellow 30 gauge needles (outer diameter 0.3 mm) which are ½ inch long, and used 2 ml plastic syringes. I bought the needles
here in the UK. In the US,
Amazon appears to stock them.
It's usually a good idea to inject a 1 ml volume of liquid slowly over a period of 60 seconds or so. What I do is squeeze in around 20% of the liquid, then wait for 15 seconds, and then squeeze in another 20%, etc, until the whole 1 ml is injected.
Hospira bacteriostatic water can be bought
here in the UK, and
here in the US. There are brands other than Hospira as well.
Would it make sense to use the regular needles to put it into the Bacteriostatic water and then use a filter needle to extract it from that.
I've never used filter needles, but I think you would just use those for the injection itself. When you are pushing needles through the rubber stoppers of bacteriostatic water bottles, it blunts them a bit, so it is a good idea to use a fresh sharp needle for injection.
If you are being fastidious, you can disinfect the surface of the rubber stopper of the bacteriostatic water bottle with an alcohol disinfectant before pushing in the needle, to minimise introducing bacteria into the bottle via the needle insertion.
Note that you never remove the rubber stoppers on bacteriostatic water bottles; to add or remove solution to the bottle, you push a needle through the stopper, and then squeeze liquid in, or suck liquid out, with a syringe attached the the needle.
Incidentally, since I did not use filter needles, what I did to minimise the amount of glass fragments getting into my vaccine vial is to hold the vial at about a 30 to 45° angle to the horizontal while snapping it open, rather than holding it vertically. If you hold it vertically, it makes it easier for the fragments to fall downwards by gravity into the vial.
Good luck!