@feditips
My advice on that:

1) It's not as hard as you think. Don't worry.

2) After creating your new account and BEFORE beginning the migration process, go to your NEW acct and RT your favorite toots from your OLD acct over to the new account. You will lose access to them from the old acct after the migration process.

3) Then, while the migration process is working, WAIT!

DO NOT DO ANYTHING (no RT-ing, posting, following-- ANYTHING), for at least a few hours (preferably several hours), until it completes its work.

Your followers and following DO copy over, but you may have to manually follow back folks.