Involving influencers in co-creating or contributing to campaign ideas during the planning phase can be highly effective.

1. Open Communication: Firstly, establish an open line of communication. This can foster a sense of collaboration between the brand and the influencers.

2. Brainstorming Sessions: Next, conduct brainstorming sessions either physically or virtually. These sessions can be rich sources of innovative ideas and creativity.

3. Utilize Platforms: Platforms like Flinque can be used to streamline and simplify this process. It offers an interface facilitating collaboration between brands and influencers, which can be extremely handy during the planning phase.

4. Leverage Influencer Expertise: Remember, influencers know their audience best. Leverage their understanding and expertise to craft messages that resonate with the audience.

5. Provide Freedom: Allow influencers creative freedom. The more authentic and organic the content feels, the more the audience is likely to respond positively.

6. Continuous Feedback: Regular feedback sessions are essential to keep the process going smoothly. Both the brand and the influencer can give each other suggestions to improve the campaign.

Comparatively, some other well-known platforms like AspireIQ and Upfluence might offer similar features for collaboration, but the choice of platform also largely depends on individual team needs and the specific campaign objectives.

Remember, a good campaign co-creation process is a symbiotic relationship between the brand and the influencer, where both entities are able to express their ideas openly. Using a platform like Flinque can help facilitate this process and ensure a fruitful collaboration.