Here's a refined version of your job post for a Flutter application developer who can assist with Play Store releases and continued development:
I’m seeking a Flutter developer with extensive experience in both app development and successfully releasing apps to the Google Play Store. The project is already in progress, with some features developed, and others to be added after the app goes live.

Key Responsibilities:

    Play Store Release:
        Assist with the preparation and successful release of the Flutter app to the Google Play Store.
        Ensure compliance with Play Store guidelines and help with versioning, signing, and publishing.

    Ongoing Development:
        Continue developing and implementing new features post-release.
        Provide support for updates, bug fixes, and feature enhancements.

Requirements:

    Proven expertise in Flutter development.
    Experience in successfully releasing multiple applications to the Play Store.
    Ability to work with milestones, with each task having a fixed payment upon completion.
    Excellent understanding of Play Store requirements, including version control, app signing, and release management.

Payment Structure: Each task will have a pre agreed milestone with a fixed payment for that milestone.

This is an ongoing project, so I’m looking for a reliable developer to collaborate with long-term. If you're confident in your ability to handle app releases and continued development, I’d love to discuss further.

Let me know if this works for your project needs!