Decided to put this together because I was bored.
GAME STRUCTURE: Chapter 1: GO, GO, WASH Chapter 2: FIX, GO, SORT Chapter 3: GO, FIX, SHUNT, SNAP Chapter 4: PAINT, GO, MATCH, GO Chapter 5: SNAP, GO, GO Chapter 6: SHUNT, GO, GO Chapter 7: SORT, FIX, WASH Chapter 8: PAINT, GO
At the start of the chapter, between each section, and at the end of the chapter, there is a skippable cutscene. Press Start on your DS as soon as the "Chapter X" words have come up fully on your top screen. If you do it as quickly as possible, you shouldn't see any image on your bottom screen before it skips.
GO: The most common segment. Just spin it as fast as possible and hope for the best. Try not to get an RSI.
WASH: 3 steps to this one: Wash, Spray, Dry. For wash you need to ensure that every bit you go over is completely covered in the soap, no partially brown spots peeking out. Doing it all in one go rather than having to go back and go over bits will save a lot of time. Spray is similar but should be quicker. Just make sure you get all the suds at the top and bottom. Drying is harder to see but is the quickest one. You don't need to go over it as many times as wash and spray. For each section, you don't need to cover every bit of the train, but doing it all as you work your way along it will save time, as it'll just stop you before you get to the end of the train if you've done enough.
FIX: Fairly self explanatory. Just move the component quickly to the train and hold down on it as soon as he says fix. The second fix is the hardest one I've found, as I often miss the target when moving it on. I've found it's best to aim a little too high rather than too low for this one.
SORT: Sort will have 24 items come across the conveyor belt and ask you to sort them, as they go faster and faster. In reality, you don't need to sort them correctly at all and only need to actually touch the last 4 or 5. The best strategy is to either count them carefully and then just move the last 5 into the red box as they come on screen, or don't bother counting and just sort them all into the red box as they come on screen. No time loss on this game for not sorting them correctly.
SHUNT: Same exact strats as go. Just spin it as fast as possible. It's faster going as fast as possible and missing the window, than going slower and making the window.
SNAP: Easiest segment. It's faster to do nothing at all. Just wait for all 30 pairs to flash across the screen without pressing the snap button a single time. You don't even have to count them if you don't want.
PAINT: Similar to wash only a lot faster to cover the whole area. Make sure you go fully to the top and bottom and don't miss any small patches on the body.
MATCH: Probably the game that requires the most practice, but can give the biggest time save. I've found saying the colours out loud to myself helps me. Do your first guess as quickly as possible and then always carefully check the first card you flip over from then on. It saves a lot of time doing this game as efficiently as possible and doing the least amount of flips, rather than just flipping over the cards quickly, so take your time.
That's really the gist of it. A big thing to remember is that it's an any% speedrun and you don't actually have to win any of the games to complete it. Try not to break your bottom screen by pressing too hard during the go sections. It should take around 11 and a half mins to complete, so aim for that on your first playthrough.