You mention time... good looking sanding is tough to rush, there's no hacks to cheat it except tossing the paper when it dulls.

Buying a Hutchins DA for one car would be considered overkill for this guy. I make a living mercilessly using a cheaper plastic version. The specs on the sander you linked did not have an indication of the pattern. Knowing Hutchins, the pattern is small. Better for primer and old finish feathering, not as good for material removal and metal prep. Sanding clear prior to buffing, with a DA, will not turn out quite as mirror-flat as using a block but the sandscratches could go away quicker.

Durablocks bend and stay bent, and as such they can lie to you. Watch that, and straighten the long ones with your hands prior to each use. Like using an engine diagnostic scanner doesn't make you a mechanic, Durablocks don't make you a bodyman. I prefer rigid tools for initial shaping of filler.

Hutchins #5504, "Speed File" is a very honest medium sized block that I like, and that you kind of described. Has a 9" foot.

Norton paper is what lots of folks around here use for blocking and DA sanding. It's good sandpaper. Shop around.

 

my go to hand block is the 9" hand file wooden handle aluminum backer, its very stiff and super accurate after that its the full size hand file same thing but longer ,it takes the full length file paper (stickit paper) Norton paper IS good but fandelli file paper is a cloth backed sticky paper that lasts just as long and priced much better both are excellent you cant go wrong with either. You really want a cloth backed paper for your shaping 36-80 grit.For your finishing grits paper is fine I like the rolls of 180-320 that you just tear off any length you need. Sorry cant help you with your patients but you'll need lots of that too.
post as you go maybe we can help make it a bit easier.

 

In other posts/forums, I've heard people swear by the 24 inch durablock.

Is that amount of length necessary? Seems a bit unwieldy to me.

Hutchins makes a 16 inch sanding board (AF-16). Would that be long enough for all the surfaces on my Camaro project?

 

Never used one never had the need the 16 " is plenty long enough to get my work super straight. it cant hurt though I have a box full of blocks I never use any more once in a while I pull one out just for one spot, I think that 24 is one of those. You need stiff blocks to get things straight. A stiff block sands the highs off of wave, a softer block follows them.
if you want things straight theres horizontally straight and vertically straight. On your 68 you need the stiff blocks to get it horizontally straight and a softer bendable block like the dura blocks to get it vertically straight. Once you start sanding it'll make more sense. Most important is guide coat, wether you use rattle can or powder it'll make things much easier and faster.
Your filler brand is very important too, never use the auto parts store "bondo" in fact Evercoat is the preferred brand by 90 % of the pros. Myself I;ve liked the Z-grip for the last 30 years or so but some like the rage gold ,I think you might find the gold a little soupy and end up with it all over your arms and the floor the Z-grip might be a better choice for someone with less experience it also sands easy and costs much less.

 

We don't get around much. Don't get me wrong, Durablocks can get you there with practice. Seriously, I do well shaping with plastic pipe wrapped in sandpaper in some areas on big tough panels. But for all practical intent and purpose, you could use either the soft 24" or hard 16" overall. You will want the Durablock set and in my opinion the AF-16 you mentioned. It would be nice to have all plus the 24". I do, but I don't have a full length hand file. There's a place to use them all and more. But if you could only buy one block, that #5504 that dead and I both like so much would be it. In the right hands, it will do. PVC pipe can make a mirror out of it. Durablocks by themselves will please the untrained eye but a long rigid block wins at the car show. By no means am I suggesting you make it a show car (unless thats the whole idea), just pointing out that sometimes the best thing isn't necessarily store - bought and labeled sanding block.

 

I have an awesome 3M 24" block. Never warps and has a rubber pad on it yet remains hard and straight.

If you don't do the work all the time a set of Durablocks will be fine, just learn which block is best for which contour you are addressing. At this point, the blocks aren't gonna do the work for you, you are. Having a fancy or better block isn't gonna do you much good. I'd get a cheaper DA too. No need for a hutchins, but it probably is a good DA.