While playing solo on a 3-day job, you can continue playing only the final day for the large payout. This is done at the card selection screen after a card has been revealed. The message "Press A to Continue To Menu" will show at the bottom right of the screen. Rather than pressing A, press the "start" button and select "Restart game". This will allow you to restart the last day played. You'll keep any XP and cash you earned already. To earn XP quickly using this exploit, play the mission "Rats" and keep replaying day 3. In that mission, you'll run to a bus and kill the mendoza gang. This can be completed in 1 minute and earns you a good chunk of XP (>11k with 2 yellow stars) and about 50k in cash without grabbing any bags. In about 30 plays i went from level 40 to 50 and gained a million in cash.