Hey, so, I've never really made a solution before, but I figured this one was pretty straight forward so I thought I'd write up the bronze times because I just went through them, and if I had known the times beforehand, I don't think it would have seemed as scary. Honestly, some of the times that jump from silver to bronze is a HUGE gap, so you've got time.
Most of these are easy, and oddly enough, the key to Bronze medals in this game is taking your time. Most lost time is because you're trying to rush something and then get all garbled and fall down a cliff. PAUSE THE GAME. LOOK AT YOUR MAP. Seriously, you don't lose time when you look at your map and when you know what is ahead, it is really easy to find the quickest route.
With the speed runs, you don't always know what exit you're are going to end up at. If you just always assume that the farthest one away is the one you're going to have to go to, you'll be set. Sometimes it IS a closer one, but few and far between, most the the alternative routes are blocked off.
For the first chapter and most of the second chapter, I used the speed gadget because the obstacles are on the ground, but at a certain point in the second chapter, you'll probably want to switch to the magnet. With the magnet gadget, you'll find yourself completely skipping obstacles and areas that you couldn't otherwise, saving you tons of time.
(if you have any more suggestions if I messed something up, let me know and I'll fix it as quick as I can.)