Jenkins Artifactory plugin not downloading in multi-thread
You could try to run the artifactory file upload in parallel if you are using the Jenkinsfile syntax: https://github.com/jenkinsci/pipeline-examples/blob/master/pipeline-examples/parallel-from-list/parallelFromList.groovy

Here is a simpler example to run things in parallel if you only have a fixed number of things you want to do in parallel:

parallel (
    "task1" : {
        //runTask1
    },
    "task2" : {
        //runTask2
    },
    "task3" : {
        //runTask3
    },
)


This can be enclosed inside a node, in which case they would all share the same workspace or each command can define node inside the task code to run into another node in which case it would have a different workspace for each task.