OP mentioned doubling the bankroll. I don't think it's a difficult task. For example, if someone has a $10 bankroll, to double it, they'll have to turn the $10 into $20. So, if you divide the $10 into $1 for each bet, it could take some time to turn the $10 into $10, because it's difficult to hit 10 bets with odds higher than 1.80 at the same time. Now, if you're patient and only take $1 on a bet with odds of 1.70 to 2.00, take the profit and save it. Then, bet another $1 on a game with odds of 1.90, you can make a profit if you hit. That way, in 15 games that you hit, you could have already doubled the $10. I know it's not an easy task, but it's not impossible.
Review what you have written because you are contradicting yourself. You cannot say that it is not an easy task and that it is not a difficult task in the same paragraph.
I do not engage in spot betting (except for the occasional bet in the past), so if I came across a tournament like that, I think I would bet on a single match where I could double my money, with the bookie giving me 2 to 1 odds. If I lose, I lose 1, but if I win, I win 11 (10 from the prize plus 1 net from doubling up by winning the bet). It's totally EV+.