You can just write your descriptor on your paper. For example, if you use Bitcoin Core, you can import keys like mentioned in topic
https://bitcointalk.org/index.php?topic=5372405importdescriptors "[{\"desc\":\"tr(cMahea7zqjxrtgAbB7LSGbcQUr1uX1ojuat9jZodMN87JcbXMTcA)#tnrke5yz\",\"timestamp\":\"now\",\"label\":\"taproot\"}]"
importdescriptors "[{\"desc\":\"tr(cMahea7zqjxrtgAbB7LSGbcQUr1uX1ojuat9jZodMN87K7XCyj5v)#xpd75frm\",\"timestamp\":\"now\",\"label\":\"taproot2\"}]"
You can use classical WIF's, you can use classical public keys, also xprv (and xpub for watchonly) should work. More complex descriptors will probably be available in the future, if they do not work today.