Let's start with statement that absolute most of these pseudo-scientific courses to increase your IQ and brain capabilities, to "unlock" more parts of brain, or make you super sensitive and similar things - are scam.

But that does not mean you can't train your brain. The nice concept to demonstrate and introduce this "percentage of brain working" (that are totally misleadingly used in pseudo-science scams and some movies) and learning overall might be neural networking from computer science:

It was originally designed to imitate network of neurons in brain. The neurons are connected with some parameters that control the throughput of the signal between them. From multiple inputs, the signal would go travel through the network to the output(s) and the most significant output. If the output turned out to be wrong, the parameters are reconfigured - repeatedly, until you have a result that fits.

That creates the significant paths in network with higher throughput. For most common combination of inputs, neurons in these paths are used while neurons outside them are not used that often - from this: the percentage of brain used. Yet it's very flexible to new stimuli.

This is just a model and brain is incredibly complex, but things like muscle memory works pretty much this way. A lot of things can be learned by repetition.

As an example: on high school, I was into memory tricks. It starts with a simple mnemonic techniques to memorize list of words, phone numbers etc. After months and something I was able to memorize pack of (32) cards with about 1 second for each and tell them in order and backwards. It was not about memorizing the cards, but about the training the mnemonic and using them naturally.

This ofc apply on all the scale of "logic game that increases your IQ and memory". You do one thing over and over and learn to think in the sets of abstractions that game closes you in. No magic, no brain evolution.

Wort to mention the best motivation for learning is enthusiasm and interest. Alot of these scams profits from small improvements that please, which makes you more opened to the concept they present - but are also absolutely natural.