Step 3: Add the brush applicator to the bottle and use
For the ideal fit, slide the open end of the heat shrink onto the bottle's tip and heat the area over the tip to shrink it perfectly to the shape of the nozzle. Also, to minimize waste in the applicator, try to minimize any distance between the tip of the bottle's nozzle and the bristles of the brush head.
Invert the bottle and squeeze gently. It may take some time for the brush head to 'wet'. But only do this when you are ready to work with the applicator, since the glue on the brush will begin to set when it is exposed to the air. For this reason these brush applicators are single-use only.
Squeezing too hard could send the brush applicator shooting off ot the bottle's nozzle (and messing CA glue). You shouldn't need to put THAT much pressure on the bottle. Perhaps even glue the applicator to the nozzle (temporarily).
The same applicator can be used on syringes when they are the method of dispensing the CA glue. Heat shrink with a diameter of 4 mm should be used for a brush that is meant for use with a syringe. I have an instructable on using syringes for CA glue storage and dispensing - http://www.instructables.com/id/Cyanoacrylate-CA-glue-storage-and-dispensing-usi/