Mass loading user for responsibility assignment

We are using EBS 12.2.4

We will be doing physical inventory soon. We have created lots of new responsibilities for the physical inventory. There are maybe 180 people need to be assigned to various of the physical inventory responsibilities. What would be a quick way to loading these other than manual data entry? We thought of using data loader, but for existing user with lots of  existing responsibilities assigned, data loader does not work well and frequently error out. Gurus, please advise. Thanks.