I used multibit years ago - now what? (BTC, BTG, BCC etc...) I have some old wallets from multibit era (~2013).  There is no way I can now download the full blockchain, so I need to import these keys into somewhere.  Worse still, I also need to import the same keys for BCC and BTG.

Try as I might, I can't seem to find clients that allow me to import old base58 keys.  I have a few files called something.key which came from multibit and are human readable with the private key in.  Everything seems to be "mobile" and "QR codes", "passphrases" and whatnot.

It's not a lot of money, and fragmented over multiple wallets, so with transaction costs stupidly high now, sweeping is infeasible.

How can I spend these old coins?  Is the only way to free up 150GB and wait?



Edit:  Ultimately I just want to create a transaction from all these wallets, to send the coins to an exchange.  So sweeping to a new wallet just doubles all my transaction costs for no reason.  Also I need a way to repeat the process for Bitcoin Cash and Gold...

Is there no simple tool to just "create" a transaction?
So I found a solution that worked for me:

BTC
Blockchain.info have online wallets but you can also just create your own transactions without using their wallet.  Add an address using import and then spend them directly using your private key.  You can manually set the fee and i managed to transfer with ~75sat/byte even though recommended was 225.

BCC/BTG
Transaction costs are still small for these so sweeping works fine using practically any wallet.