I made a supportless citadel paint holder to transfer into 15ml dropper bottles using included funnel in the common kits you can buy. Compatible bottles pictured for reference including dimensions.
Fairly easy to use, insert empty bottle, funnel and open citadel paint pot upside down and then flip it over and watch the magic. You can use flow improver, airbrush thinner or water to help first just mix a bit in.
Have fun!