Marketing and advertising for those who haven't been trained in a retail-based office environment that depends largely on a sales force to survive is pretty much an enigma. To those of us who know its intricacies its a simple matter of understanding the product, the market and the customer. Then it's only necessary to target things in the right way and you have a success on a plate, or more likely a failure.
I've seen more marketing executives jump under a bus, figuratively speaking, than I've seen succeed in achieving their aims. Instead of a hit & miss affair it's more of a 'miss, miss, miss, miss, hit, miss, miss, miss, miss' one. There are few (very few) advertising companies out there who boast of multiple successes with their clients. What they don''t tell you is how many advertising gurus the system ate, chewed and spat out to get them there.
Writers are writers, they're not marketing or advertising gurus, they write, fullstop! The only trouble for everyone is there is no guaranteed marketing plan that will work for more than one person at a time. They have to be individually tailored and tested, tested, tested and if word gets out that something works, then it's everyone pile onto the bandwagon until it caves in under the strain. Those who have a working strategy aren't going to tell you and me about it. My point to all this is, there is no easy or reliable strategy to get your book sold. You have to find your own way and whilst all those courses will teach you to do A, B, C if everyone does it the same way, you will all arrive at the point of failure together. Learn how others do it, but not with the intention of copying them. Learn the methods, techniques and strategies and then design your own and test it to breaking point until you get it working for you.
THEN, MOST IMPORTANTLY, DON'T TELL ANYONE WHAT YOU ARE DOING RIGHT.