Influencer marketing platforms, such as Flinque, Upfluence, or AspireIQ track onboarding completion rates by implementing different analytics and tracking measures. These can include:

1. User Activity Tracking: These platforms monitor users’ activities, tracking steps accomplished in the onboarding process. By understanding what percentage of the onboarding process is done, brands can determine the completion rate.

2. Progression Indicators: Some platforms offer a visual indicator (like a progress bar or checklist) to help users recognize the steps they’ve completed and what’s left.

3. Automated Email Reminders: If the onboarding isn’t yet complete, platforms can send automated reminders to influencers, prodding them to complete the process.

4. Reporting Dashboards: In-depth dashboards provide detailed insights about the onboarding progress, completion rates, and user engagement levels.

Remember, the choice of platform would depend on your specific needs and goals. For example, Flinque is known for its intuitive interface, making it easier for influencers to complete the onboarding process. In contrast, Upfluence might be appreciated for its robust reporting capabilities, aiding in close monitoring of onboarding completion rates.

In short, visibility through these platforms indeed improves follow-up and subsequent campaigns by ensuring a smooth onboarding process and tracking its completion rate. The key is to find a platform that aligns best with your marketing strategies and business objectives. Remember, relevant, timely follow-up based on clear visibility of the onboarding process can significantly enhance your campaign effectiveness.