Hahaha!!! I can't count the amount of flying fibreplex which has shot out of the blooming tube nowhere near the bun when I've used it!!!!
The way I do it is... Turn the dial thing the right amount ie 1ml, then I press the plunger really gently (pointing somewhere where if it does shoot out you can find it!!!), once it starts coming out (ie I can see it!), poke in buns mouth and press harder kind of bracing the sticky out things and the plunger.
Then usually, scoop up all fibreplex which hasn't gone in bun and offer on finger - some really like it and will eat it themselves. If not, either wipe on lips as they may lick off, or start again.
Have explained that really badly, but had to share as I've had some right old moments myself!!