I worked in investment banking for a few years and learned how to build pretty detailed financial models, I also learned pretty quickly how useless models are as an investor. There are too many variables that need to be forecasted to make a DCF effective; add that to the fact that in most cases most of the value comes from your terminal value assumptions and what you get is a mechanism to spit out whatever value you want.
Having said all of that, I'm relatively new to taking investing seriously and have done a lot of reading. Almost everything on value investing suggests forecasting is useless. I struggled with this idea because in the absence of forecasting, I wasn't really sure how I can measure intrinsic value, which is required to measure your margin of safety. I than came across Bruce Greenwald's from Graham to Buffet book and he presents some more reliable ways to measure value: replacement value and earnings power value. Obviously like all valuation models these have their flaws but they seem less flawed than DCFs so maybe take a look at that as well. I would also be interested to learn how most other folks on the forum measure their margin of safety because there are a lot of really smart people here.
Apologies for the digression, to answer your original question, in addition to the McKinsey book, I would also check out the Scoopbooks Series on Investment Banking. They have a good book that goes through DCFs and is a bit more practical than theoretical.