So basically I want to sell lukes fork coins from my cold wallets, which are secured by musig and shamir without the need to type my private keys into shady wallet forks.
The idea is to minimise risk by distilling everything to a single point of failure, split it and send all bitcoins back home to safety.
Here is how to do it:
First and most importantly you need a malware free system with a recent version of electrum. this is the single point of failure because we will create a jumpwallet, which will contain all our bitcoin for a short amount of time.

1. create a new wallet in electrum & write down its seed. this is our jump wallet.
2. move all your bitcoin to that new wallet. most impoirtant part is, that they need to move ON BOTH CHAINS.
   to make sure this worked fine you have to do the following for all your cold storage bitcoins:

• create a tx which moves everything to the jump wallet.
• then go to mempool.space and search for tx id. it will be found because you just broadcasted it.
• now go to mempool.guide (Lukes fork version of the same page) and search for tx id as well. If its found, you are golden. coins moved on both chains.
• if it is not found on ck to mempool.guide, which happened to me in most cases, go mempool.space. In the "Details" section, click the link next to "Transaction hex" and copy the hex. now go to https://mempool.guide/tx/push paste your tx hex into the first text area and click on "broadcast transaction" this way your tx is broadasted to the forked chain as well. if a red text appears next to the button something went wrong and it tells you what. if everything went fine you'll find you txid on mempool.guide as well, which means your forked coins moved.

3. Now you have all your bitcoins and all your forked coins in your jumpwallet. whats left is creating a tx which is valid in bitcoin, but not on the forked chain. We will do that by sending all coins to ourself and add a op_return.
4. in electrum, go to the "adresses" tab and copy the next free receiving adress of you jumpwallet. now go to the "send" tab, click "Tools" and select "Pay to many".
5. enter whe following 2 lines into the "Pay to many" textbox:
   YOUROWNADRESS, !
script(OP_RETURN aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa), 0

the syntax is simple, its target followed by amount, seperated by a comma. the exclamation mark means "everything in this wallet minus fees". So first line sends everything in the wallet to one of the wallets own adresses. the second lines sends 0 aka nothing, to an OP_RETURN output. what exactly you write into op_return is not relevant as long as its over 80 bytes of hex. hex is 0-9 and a-f, and 2 hex letters make a byte. so i simply went with 180 time the letter a to get a 90 byte op_return, which is not valid on the fork chain and will be rejected, while it confirms fine on bitcoin.
5. sign and broadcast et voila - you successfully splitted your coins. you can try to paste and broadcas the tx hex in https://mempool.guide/tx/push for fun but it won't work, because its not valid.
6. all thats left is move your bitcoins back to where they belong and wait for confirmations. now you can import the jump wallet or sweep its private keys into shady fork wallets and your bitcoin stays untouched. disclaimer: the airdrop-frenzy in 2018 teached me that shady fork wallets often contain malware so use them in isolated VMs only.