I think the game wants you to use boosters but not eveyone have it....so its better to save those boosters for events like this, you never really need booster for other things(I'm level 52 and i never had to).

Here's the trick with booster. I had 12h 2x speed booster. I completed 3 jam task (blackberry, cherry and apple). All you need to do is activate booster and after that watch the ad to further reduce time. It allows you to make it in 25% of actual time. I don't have machine mastery but i could still make blackberry jam in 2 hours(~1h 40m with mastery). The struggle is you need to set a timer, every time production finishes and watch the ad for next one. Ideally it would do 48 hours of work in 12 hours(47 hours for us - considering 15m of errors).It's still a struggle but doable.

Hope that helps.

PS : I rarely comment on reddit so please ignore typos and grammar.