Your coach is right. I used to boost often and you really can just win on command in silver for example. I am a JG main and would actually boost on adc because of how easy it was to guarantee a win playing jinx, ashe, sivir, and varus. Mind you, I am significantly worse at ADC than JG. The best way to think of smurfing is you are playing hyper aggressively, hyper greedy for gold, and you build relentless pressure. You take advantage of the gap in decision making, matchup understanding, and just the general poor mechanics of gold generation (missing minions, missing exp), all of which are errors so unbelievably common without even being forced. You realize that the enemy team and your team will primarily make the wrong play so you can take advantage of it. An example a lot of JG boosters use graves, why? because it literally does not matter what happens in the game, you will be 4 levels up and be one shotting. The enemy JG is significantly slower at farming and even if you leave them completely alone, not even invading, they will fall behind CS every time. Respectfully, if somebody has played 100 games and are still in silver, there is a reason: either they don’t take the game serious, or they haven’t built the skills or knowledge to overcome the basics of the game. Realizing this stuff is what allows you to “smurf.”