Upshift double-clutching is useful to get it smoother, but I find that winding it up to around 4.5-5K in first, and then 'staggering' the shift a bit is much easier. Beyond 1>2, I don't find it necessary. Downshifting is different; double-clutching definitely makes the shift smoother, and it's really, really easy to do in the 8. I know, I know, that's what synchros are for, but old habits die hard (especially when you've had a glorious synchro fail...).

Zenmoused: you're talking about heel-and-toeing, which is very nice to learn for the track, and perhaps somewhat useful for spirited driving, but is quite easy to mess up and get distracted. Practice makes perfect, sure, but in this case, unless you do go to the track, it's an extra. Besides, unless you want the lower gear in much, much, higher revs, there's little point with the 8 in most situations.