How you handle the weeds depends upon the kind they are. If they re-sprout after they're cut down, you need to remove the roots or kill them with an herbicide (weed killer) which kills the roots for you.

The problem with using herbicides is that it's too late in the year for them to work.

When it comes to the trees you cut down, some may also return. If conifers (pines and the like), you're home safe. If broadleaf trees such as oaks & maples, they'll return from the roots.

For broadleaf trees (already cut down or not), I suggest you let them grow next spring then, in July, cut them down and *immediately* apply a systemic herbicide to the cut surface of the stump. Repeat as needed.

You said "In other areas I've removed the top 12 inches of soil and replaced it with bought topsoil. I'm feeling like that's a waste."

I agree that it's a waste. Don't do any more of that.

If you were trying to get rid of weed seeds, more will arrive by wind, birds and more.

Regarding poison ivy (or oak or sumac,) the urishiol (oil which causes the rash) is still effective in crispy brown leaves for a while, and also on the dead/dormant vines, and roots. Please educate yourself more comprehensively before you attempt to work with/around it.

Personally, I love dry stone walls as they have huge potential for growing various ferns and other treasures. You might also want to construct them with soil in pockets on top for planting things that require excellent drainage.

Have you decided on your overall garden scheme? If you plan to use a lot of shrubs, or develop the woodland, then the sooner the shrubs are in the sooner the bones of the garden are developing. You can always take out the sheltering nurse plants when your treasures are established.

If you clearfell a lot of scrub then the weed seeds in the duff will respond to the extra light, warmth and moisture - and you'll be fighting the green tide. It can be more effective to clear smaller areas, intensively weed and mulch, plant into annuals that you weed frequently to repeatedly reduce the fresh weed burden.

If you are a stay at home serious gardener then a 300' strip won't seem too bad. If you have entertaining to do, or a business to run, you'll be forever in catch-up mode, and that's no fun.

Cardboard needs to be laid overlapping to exclude the light. It can work. So can old jute-backed woollen carpet. (Well, any carpet, really, but it can be yucky when it degrades.)

If you like them, then conserve any natives and ferns that may have settled in. 'Free' groundcover for now.

Learn your local weeds - and how to deal with them. Something you might have previously treasured can turn out to be a serious thug in a new location. It doesn't even have to be declared noxious for it to be a bane in a particular garden. (Solomon's seal and bluebells...aaaargh!)

You might find a mattock to be a useful addition to the toolkit. Well-sharpened for hacking through roots, and also good for prising out rocks.

If your garden path system is still primitive - you might find that a sturdy vinyl tarpauline with rope handles at one end is of much more use than a barrow or cart for hauling away slash, weeds, and even small stumps.

Truly sounds like a lot of fun - but I think I'll keep the thistles and blackberry I'm currently tackling. I wouldn't know what to do with poison ivy!