L8E is one of the more difficult step of the PCMS method, and unfortunately there currently exists no consistently very fast way of solving it. The best methods as of now are as follows:
- Solve two opposite D-layer edges so you're left with LSE
- Solve three D-layer edges and being left with L5E
- Solve all four D-layer edges and being left with ELL
- Solve EO and then continuing however you see fit
If you want to get as fast as possible at L8E, it's probably best to familiarize yourself with all of these methods and just make a quick decision following CMSLL on which method would be best to use for the solve.