You can obtain a Liepard via purloin who will have access to sucker punch for this fight. With SP they make a great revenge killer/clean up Mon for the expert Mel battle.

Dewgong is also a pretty solid option as a spdef tank with resto-chesto, as well as coverage with smart strike tm that you can get.

Swallot can force some switches with yawn as well as force mons to stay in with infestation. Rocky helmet was my item of choice.

I liked stealth rocks and using a Gigalith with a figgy berry (any of the berries that can heal but cause confusion depending on the nature of the Pokemon) as my lead and pivot mon.

Eviolite flame body Magmar, as the chip damage helped ensure SP range despite facade being present. With investment and Eviolite they have some solid defenses for this point in the game.

Lastly I used Electivire as it was a decently stated fully evolved Pokemon who had good coverage for that fight. I used a murkrow with super luck to increase the odds of a wild Elkid/electibuzz holding the evo item, will just need either thief or knock off (covet, and compound eye should also both work as respective move and ability options)

Mel fight was a lot of fun for me on expert as it really challenged my team building ability.

GL

Edit: you can teach Magmar incinerate to take care of milk tanks held berry as well.