In this message I only mentioned the fees.
It's a straight forward process, but it seems to be more work and steps than it could have been.

Sell Forkcoins on Bitpie
1. Use Bither to import the private key, and send the Forkcoins one by one to it's deposit address in your Bitpie wallet (wait for confirmation)
2. Switch to Bitpie
3. Click Exchange (at the bottom).
4. Select the Forkcoin (say BCD/BTC) (at the top)
5. Click Sell
6. Click Deposit, this brings you to Pie Bank
7. Click Deposit, now you Deposit BCD from Pie Wallet to Pie Bank (wait for confirmations)
8. Go back (to the Exchange), click 100%, click Sell
You now have Bitcoins
9. To withdraw them, click on Buy, then click Deposit. This brings you to Pie Bank again. Click Withdraw to send your Bitcoin from Pie Bank to Pie Wallet (wait for confirmation).
10. Go back to your Wallet, choose BTC, click Send and send it to your normal wallet. Set Miner fee options to -2 for 0.0001BTC fee, this is more then enough at current fees. Bitpie can't go lower than this.

After writing this down, it's not straight forward at all, it's an annoying amount of work for something this simple