Put the collard greens and kale in a large microwave-safe bowl and drizzle with 2 tablespoons water. Cover with plastic wrap and poke a hole in the top to vent. Microwave until the greens are just wilted, about 3 minutes.
Whisk the chicken broth, flour and Cajun seasoning in a 6- to 8-quart slow cooker. Add the black-eyed peas, celery, scallions, andouille and bacon. Top with the wilted greens and gently press to submerge the ingredients in the broth. Cover and cook on low until the black-eyed peas are tender, 7 hours.
Remove and discard the bacon. Lightly season the shrimp with salt and stir into the stew. Cover and continue to cook on low until the shrimp is cooked through, 3 to 5 minutes. Season with salt. Serve with rice and top with hot sauce, parsley and more scallions.