Quoted from redditor Fulvio55:
All you need is a text file to put your wallets in, like this example from https://walletgenerator.net/?currency=Dogecoin
Use https://coinb.in/#settings to move coins. ELI5. Download both sites and run them offline.
Use https://bitinfocharts.com/dogecoin/ to check balances and transactions.
See this guide or this video for coinb.in tutorials.
And read the ELI5s (and my history) for more info.
Basically, if you have your keys, you have your wallets. You don't need to do anything other than keep them safe. That's it. No software, no third-party services, nothing else required.
Now, one small gotcha. Dough has been a problem from the very beginning. I would definitely check at least one of those keys if I were you. To do this is quite simple, luckily. Just go to coinb.in and instead of putting in the wallet address, put in the key and hit load. Check that it comes back with the same address you were expecting, and that the transactions it loads match up with what you were expecting as well.