If you're making your own pack, you don't need the default textures. Just make your own. The information on how to set things up is on the Optifine GitHub (https://github.com/sp614x/optifine/tree/master/OptiFineDoc/doc). Look at ctm.properties in particular.
If you're not sure what to do still, ask specific questions here. You can also try the All-Inclusive Guide to Texturing, though anything it has on CTM is probably a bit outdated. Finally, you can always try cracking open a resource pack that has CTM and try reverse-engineering it. Ya'know. See what that person did and then try adapting it.
I hope that helps you.