Well this took a lot longer to fix than I was hoping for. In this video I attempt to repair the annoying overly gunked up hotend.
If your gunked up hotend is not as bad as mine, you may just be able to heat it up to extrusion temperatures and carefully remove and clean everything. Unfortunately, that was not the case for me.
I ended up having to replace more parts than I was hoping near the beginning of the video. Below are the parts I used (affiliate links – no extra charge to you)
Micro Swiss All Metal Hotend Kit for Creality CR-10 (for a full replacement and to skip a lot of this work): https://amzn.to/2CU4SDM
Stock Hotend: https://amzn.to/2NDAp0A
CR-10 Heater Block (you may be able to find a better place): https://amzn.to/2MgcAr7
12V 40W Heater and Thermistor Replacements: https://amzn.to/2Oavsta
Silicone Sock: http://bit.ly/2MmUNOO
Plated Brass Wear Resistant Nozzle: https://amzn.to/2CLpsG9
Standard Brass Nozzles: https://amzn.to/2p13t4m
E3D Parts (if using this hotend): http://bit.ly/2JFaUen
Solder Seal Wire Connectors: https://amzn.to/2O8oULD