Thanks Foxpup, so..

* Use freshly minted coins (hard to get significant quantity from miners)
* Send coins to different accounts you own on each chain (trial and error, could take a few attempts)
* Try trigger different consensus rules (not always possible depending on fork reason)
* Try find a miner who can directly accept new tx (no relay) and place in one chain only. (not many powerful miners to choose from, requires effort from them to build)

Not really any great solutions.. probably the double spend until you have coins in separate accounts sounds best.