Tips on being a Project Manager with part-time teams

Let's face the facts: nobody likes to be bossed around. Even if they only feel like they are being bossed around. This creates distance and resistance to accepting instructions and suggestions. The team that is not dedicated to a project full-time can see a project manager as another boss. So the barrier for communication and cooperation can get even higher.
Stay focused: the project manager's main job is to get the project done on time and on budget or just get the project done. This means getting other people to do their jobs, which is made worse because they see the project manager as another boss on top of their own
First, the project manager (PM) has to eat some humble pie. The ability to get other people to do their job for the PM is based on how good the skills of the project manager. Some humility mixed with steadfastness and a firm hand is required. Otherwise, it's just bullying.  Bridging that boss-worker gap helps. Here are some tips to start bridging that gap.

1. Don't use project management phrases with the team. Using them can been seen as being snobbish and distances the project manager from their team. Instead, use words that describe what they are. It's not Project Objectives, it's 'what we want this project be able to do at the end of it'.
2. Describe tasks as a smaller part of the bigger picture when it overlaps with other people's job. Often a company re-uses internal resources. This means people who are part of the organisation but not involved directly in the project or with it full-time. They become defensive if they think the project manager is doing their job or trying to take away their job. The PM has to engage them with the goal of having them understand what the project and the PM wants to achieve. They will either get out of the way or help the PM along. If they refuse to cooperate, the PM has a legitimate reason to work around them or replace them. It's best the PM document their refusal because working around them may incur additional cost.
3. Understand the team's or team member's needs in relation to the project. The project manger has to show that they know what the team's needs are and understand why. The team members will appreciate that the PM understands them and their work. In most cases they will be more cooperative but the PM has to still prepare to take a stand when it comes to the project itself. 
4. Do first the project management tasks or responsibilities that the team appreciates. Make it visible. It will go a long way if the customer appreciates them, too. Once the team can see project management tasks that they think is important being done, they won't mind the PM doing the tasks they value less (but is still important to project management).
5. Create enough documentation process or documentation requirements to move the project along. The PM must be willing to change templates that cover too much or too little. The team has to see value in the documentation. The project manager must refer to them during meetings to show that the documents are being used and is useful. The PM also has to be prepared to take action when issue arise because they weren't used. This increases it's value even further.  
6. Sign off on documents with your team. Documentation also establishes blame responsibility. The team knows that and may be reluctant to sign off on documents. Project managers should make it a habit in the beginning of the project to sign off directly below where your team members sign off. This shows that you are taking the responsibility with them.