The Big Con

From the developer's own guide, https://steamcommunity.com/sharedfiles/filedetails/?id=26526....

Step 1:
This quest begins in the Alley behind Linda's video. Open the luggage using the secret code you learned by doing a #prankcall on the Mighty Yell Discord -- (or it's 4-5-2).

Step 2:
In Mallton you'll be given a prompt to use the payphone. Call the shoe stranger and tell him the information he told you in Lisbon (it'll be in the notebook if you forget).

Step 3:
When you get on the Train, you'll be able to find a jar of shoe polish in the lead car and must take it to the garbage in the cargo car, as per the instructions.

Step 4:
In Las Venganza you can follow the instructions from the letter on the Train, and head to DeLancie's pool hall to interact with Jimmy. Jimmy will tell you where you need to go, but you might be able to do MORE if you talk to Dee, who appears outside the bar.

Here is a article that serves as a good guide: https://culturedvultures.com/the-big-con-guide-shoe-questlin...