Microinjection intestinal organoids

I am attempting to microinject small intestinal organoids, using the Eppendorf FemtoJet 4i microinjector and Femtotip capillaries, and have come across several issues. This is a new set up in our lab, and I am first to attempt it so I apologise for the basic questions.

When attempting to fill the Femtotip capillaries using a needle or Western blot tip the liquid backs up and does not fill the capillary, leaving a large air bubble. Is this a common issue with the Femtotip capillaries? Are there other methods for filling (that do not require specialised microloader)?

When I attempted to use a tip where I had let the liquid be pulled to bottom by gravity, I had issues with leakage out of the tip bottom. Just to be absolutely clear, is it necessary for the entire tip to be filled with liquid prior to injection (no air bubbles)?

Finally I would be grateful for any advice on injection pressure and time used for organoids.

Thank you