Well one needs to apply all acquired knowledge about money laundering to advance in it. For example if selling drugs, one needs to create a proper method to launder such money, through something that is already familiar ideally. For example one can launder money with workshops, clothes shops and whatever. The options are endless. One has to be creative, adapt and be careful, planning in advance. A great way nowadays is selling collectible cars. Easy to justify. Also fine arts and wine trade. Also cash only businesses like laundromats, vending machines, arcades, and tip-based businesses are great fronts to mix the proceeds. Regarding these, one could also discourage the use of credit and debit cards by adding a 5% or 10% fee on top of transactions.
Again one has to be creative and careful. One has to fully understand that the process entails the manipulation of legal gains with illegal ones. Initially I got interested in the subject watching Breaking bad, season 2-3 Saul teaches the basics. However as with anything else Hollywood makes it look silly to some degree, due to the lack of any kind of deep knowledge. To make it happen one needs to have a lot of business, accounting, banking, laws and tax knowledge and be very patient. So this is why laundering money is not the main activity of the business of crime, it's usually a service that takes a lot of time and "boring" knowledge to make it work.