First go to the Job Select Screen



and select Private Match at the bottom the the screen like shown above.

Next on the Stage Select screen goto the bottom:



And click on this Icon:

so that it looks like this:


Once the stage select screen looks like this:

Click on Random

Then click Start Job:

(Difficulty changes optional, but testing points to no significant changes in exp)

You may now walk away, change the channel, alt-tab out, or do anything else.
There is no afk auto kicking in private matches. You will get roughly 3,000 exp per round, give or take a couple hundred.

I watched Ghostbusters 2 and Afterlife while doing this.
Enjoy!

To replay Bounties endlessly, follow all of the above steps but stop at the difficulty select screen:
(this screen)

At this point, press Esc or B/Circle button to back out back to the main screen:

DO NOT CLICK BACK AT THE BOTTOM OF THE SCREEN TO REACH THIS SCREEN OR IT WILL NOT SAVE INFINITE ON

At this point you may select your bounty and you will be able to replay it at random locations, though you will not receive the contract rewards after the first one; all match rewards are given at the end of each round like normal.

Here's some shots of it working:



A giveaway that it is setup correctly is that you will see the location say Random Job instead of the bounty location:



Here's a video guide with demonstration:


This can be used to create conditions that may allow you to maximize exp gains per minute, either AFK or otherwise, or create ideal conditions for farming specific Hustles or Research contracts; or if you just really wanna challenge yourself with a Hellspawn bounty over and over.

Good luck, and happy busting!