zec-qt-wallet can now do one-click Sprout → Sapling turnstile migration in a privacy-preserving way. Please try it out on Testnet and let me know how it goes 
I’m planning on releasing this for mainnet later this week.
What the turnstile migration does:
- Creates new t-Addresses in your wallet to move funds from Sprout -> t-Address -> Sapling.
- Splits the funds across multiple t-Addresses over multiple blocks
- Uses round numbers to obscure any identifying information.
On Testnet, the migration happens quicker (over 6-20 blocks), but on mainnet it’ll probably be spread out over more days.
