Let's assume this is going to happen as the JWs believe.
Either there's going to be a lot of work to be done or God will do it all. Clean up all the rubble, purify the waters, etc. If God doesn't clean up, there should be remnants of the world around us still there. It's kind of like "I am Legend" with at least a few more people. There's about 1 JW for every 167 people in the US (Pew survey 0.6%). If libraries aren't destroyed, a lot of things could be learned. If supermarkets still stand, I would think there's enough canned goods, bottled water, (and for a while, fresh goods) to keep people going for a while. Enough time at least for people to find various crops and farm animals to use for food.
I don't know what the current thoughts on resurrection are. When it's supposed to happen or in what sequence, but if a few "old school" "low tech" farmers and builders were required, I would imagine God could resurrect a few to help out.
The biggest problem would be organization. People will need to teach others. How do they find each other? A city is a HUGE place, especially without cars. How are you going to find other believers to reform community? Rural areas are even worse because people are more spread out. People are going to have to take on roles. Who's going to farm? Who's going to raise animals? How do you organize that? There's going to have to be a supply chain for the goods produced. How does it get to the people who need them? What of these 144,000 kings and queens? Will they talk to us from the sky? Is that how things will be coordinated?
Of course, there is talk in the Bible of a NEW heavens and a NEW earth. Maybe we'll all be teleported to a brand new paradise planet "in the twinkling of an eye" and there'll be no cleanup.
Theoretically, it could all work out. You'd just think it'd be wise to start planning now if they really believe it. Unless they believe there will be too many unknowns. Why learn automobile technology if God might not allow it?
It's all just imagination to me. Ranks up there with fantasy scenarios like, what would I do if I could stop and start time?