The first step is to remove your valve core with a pair of pliers.
Then using a pair of needle nose pliers hold the valve core firmly on the flat surfaces you used to remove the core from the valve.
While holding the core with the needle nose pliers take another pair of pliers and while pulling outwards unscrew the brass thumb screw until it is removed
You can then remove the dried sealant with your fingers.
You can then reassemble the core making sure the two air notches in the brass thumb screw are facing the main body. After the brass thumb screw is installed you should test it to make sure it will not fall off when you unscrew it. If the brass thumb screw threads off the end you should take a pair of pliers and on the last few threads gently squeeze the threads to damage them so the brass thumb screw will not fall off
