capt!
The operation of the Mill's Front Jackpot can be a little confusing to someone new to the hobby, especially while still residing in the cabinet with the mech installed hiding its interaction with the mechanism so I usually tell those new to the hobby to remove the front jackpot from the casting making sure to retrieve all shoulder mounting bolts and the fiber washers located on them for replacing the front jackpot correctly!
After front jackpot is removed place the front jackpot in a vise so that you can thoroughly check out its operation and familiarize yourself with how it works!
Making sure that all pivot points are freely moving and not gummed up and that all the internal flaps for the main jackpot, the reserve jackpot, Etc. are operating correctly!
In a slot machine it is good to remember the old saying
"That for every action, there is a re-action" as it is definitely true in a slot machine mechanism!
As for the jackpot while mounted in the vise after checking operation it may be necessary to remove cotter keys and remove levers at pivot points for de-greasing and using proper lubrication and replacing.
As with any disassembly remember where all the parts were located prior to disassembly for replacing after cleaning, which in your case as you have two jackpots you can compare them side by side if you loose track of the configuration!
Hopefully some of the pictures below will help you with your understanding of the front jackpot!
Bona Fortuna!
MONTI