Paint Issues/doesn't seem to dry completely

Hi folks. I've gotten back into modeling after a 35 year hiatus. My question has to do with a problem I have just encountered with some paint. The paint doesn't seem to dry completely even after three days and feels tacky. I've built 4-5 kits and airbrushed them with Vallejo and Tamiya acrylic paints and have had no real problems except for the tip of the airbrush drying and spitting sometimes. I researched that issue here on the forums and someone recomended using a flow aid to help. The only stuff I could find where I live is Liquitex Flow Aid. The post I read said they used one drop of flow aid in the color cup, but I may have over done it by using 2-3 thinking more is better. Would this cause the paint not to dry completly? Did I get the wrong stuff? Is something better? I was better off before with the tip drying and spitting. I'm working on a Dragon 1/48 Fokker Dr.1 for my son and hope I can save it with a coat of clear acrylic varnish (with no flow aid). Help...Thnaks, Tom