I've never gone 2nd to 3rd but from 1st to 2nd I keep my foot down on the gas bang the clutch and smack the trans into gear. I will probably break something soon..... My guess on shifting up would be having lots of power and/or going really really fast.
Downshifting depends on if you want to lock the rear by downshift it not. If you want to break traction with it then just downshift and let the clutch out, the rear will lock. That's pretty hard on car.
If you don't want to lock the rear then you will need to heal toe to keep the revs up and not upset the traction.
I don't know if that helps.
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