I use 10ml plastic syringes with their needle, bought at the chemist's. I numbered them so that I tend to always use the same syringe with the same liquid.
I aspire the chemical from the factory flask with the syringe. I empty the syringe in the Jobo flask. I then, with the same syringe, aspire tap water from a coffee cup (without coffee, with water, that is). I empty the syringe in the Jobo flask. I normally have to do this two or three times or so. This washes the syringe inside the Jobo flask so that the small residue of chemistry in the needle goes into the bath as well, and the syringe ends up clean.

For those couple of baths when using a 10ml syringe would be tedious I use a (numbered) plastic cylinder for photographic purposes (AP brand).

When the factory flask becomes empty enough that I don't manage any more to "fish" chemical with the syringe I will put some chemical in a coffee cup and use the syringe from there. The needle in the syringe can "fish" quite deep anyway inside the flask.