1) You know all your prefork coins are also available on the BCH chain, therefor you only need blockchain data up to the fork point to move these coins.
2) You have all this data already in the form of the Bitcoin blockchain pre fork, so why not just use that?
3) You'll want to create a copy of your blockchain data then remove blkXXXXX.dat files up until the fork point . I don't know which file this is, something around 950~960, I'm sure someone will figure out the exact file. Note that if you did not move any coins post fork yet, you do not need to delete anything.
Important: If you did not move any coins post fork yet, you do not need to delete anything.
But if you do, you need to delete enough for the newest blocks such that your transactions post fork are obscured.
If you use armory on Linux, delete blocks in ~/.bitcoin/blocks
Basically, instead of clicking on the armory icon, go to /usr/local/bin to run ArmoryDB and armory manually.
But I found it difficult, what I did instead was to, while Armory was running, go to the Help menu and choose to rescan and rebuilt data base. A pop up will show up asking to confirm that you want to rescan and rebuild the next time armory starts and that it will take a lot of time. Accept.
Restart armory, and use the terminal to shut down bitcoind by running pkill bit. This way armory will remain offline
You need to be in expert mode. While armory is running, go to the user menu and select expert. Click on your wallet and select to send bitcoin. Enter the bitcoin cash address and the amounts and the fees (fees for the cash network are x10 lower, I used 20 satoshis per byte and it got confirmed really quickly.
The glob of text is a rectangular block. Copy that, and then click on Offline Transactions on the main armory window (I spent a lot of time looking for this on the menu bar and was trying to figure out if Broadcast Raw Transaction was what I wanted, but no it isn't, the button is in the main window).
Paste the block, click sign, choose the signer and in the window where you pasted the glob, there is another button like goatpig said "Copy Raw Tx (Hex)". Click that and you get a long string.
Paste that here: https://blockdozer.com/insight/tx/send
And you are done.