The reason your Finish Gel is getting thick and stringy is because Activator, Brush Softener, or air got into the bottle.
-- When you are applying the product and you get to the Activator step, apply the first coat of Activator and wait 1 minute for it to completely dry if you are using the Professional liquids -or- wait 2 minutes for the Activator to completely dry if you are using the EZ Care liquids.
-- Buff the nail and file it to the shape you desire. Brush off dust and particles or wash your hands WITHOUT soap and dry thoroughly.
-- Apply the second coat of Activator and wait 15 seconds for the Activator to dry if you are using the Professional liquids -or- wait 1 minute for the Activator to dry if you are using the EZ Care liquids, then wipe each nail with a paper towel before applying your Finish Gel.
-- When applying Finish Gel, you may want to wipe the brush on a paper towel after it touches the nail and before reinserting into the bottle. If the Finish Gel brush gets Activator on it and then goes back into the Finish Gel bottle, it will cause it to get thick. The Activator coming in contact with the Finish Gel brush can also cause the Finish Gel brush to stiffen or harden.
-- Please see this video for proper Brush Softener use, to avoid getting Brush Softener into the Finish Gel https://www.youtube.com/watch?v=8dRTbQCURxM&t=2s
-- Getting Air in your Finish Gel can be prevented with proper use of the 'wiper' inside the neck of the bottle. The wiper inside the bottle should be used to regulate the amount of Finish gel you get on the brush so that you don’t apply too much on your nail, and it also reduces the possibility of getting excess liquids on the rim of your bottles, potentially causing them to get glued shut. You can always wipe off the rim with a paper towel before closing the bottle for storage.
We recommend checking out this video for more tips and tricks that would be sure to help: https://youtu.be/dbWkaUenKcs
Your technique will definitely improve with practice!