Norman When I’ve used a single resource to represent a resource pool (more than 1 resource), I’ve done 2 things. First, I define that generic resource as a local resource in my project schedule only. Don’t use an enterprise level defined generic resource. See note. Second, I manually entered the resource Max Units in the Resource Sheet view to equal the sum total of all resources it was representing. This would be 500% in your case. With this configuration, you simply assign the local generic resource to tasks in the same manner as any other resource. The resource’s Max Units (500%) will become the default task/resource assignment units when the resource is assigned.
Note: If you are using server, you can have enterprise level generic predefined resources. Don’t use these since the Max Units gets reset back to the enterprise level definition every time you open the schedule. Hence the use of a local resource.