Step 1- Get a Female Marill/Azumarill so all of the offsprings will be of that Evo chain.
Step 2- Get a Male Pokémon with Aqua Jet, then breed it with the Mar/Azumarill until you get a Female with Aqua Jet.
Step 3- Then get a Male Pokémon with Belly Drum, and breed it with the Aqua Jet Marill.
All you need to do after that is just breed until you get the desired Marill.
Hope I helped!
Source: Experience (I've done it quite a few times now)