Transfer list them first and immediately after offer them to clubs. If you dont care about the money, try to offer them for 0 or maybe 1M over 12months or something like that.
Also, one time I was trying to offload a player but even though a few were interested, whenever I tried to offer him to clubs, they came back and said that they wont be able to accept his wage demands. So I took the player off the transfer list, played him in a couple of matches as a sub and he was happy again. Offered him a new contract with lower wages and he accepeted. Then I offered him to the clubs and they were happy to bid for him!! A few other new ones came in for him as well.
If you dont plan to play them at all in any matches, try to offer them a much lower salary, but with a ridiculously high goal bonus and appearance fee. It shouldnt matter to you because they wont be playing any matches so you wont need to shell out any money. They generally ask for higher wages and might reject your contract at first. But when you offer them again, this time they are generally happy to lower their wage demands and take the high appearance and goal bonus. Give it a shot. Might work.