Getting Your Perfect Breeders
Place 1 male and 1 female into the Propagator.
Open the Filter Settings.
Under Stats, tick every stat you want your breeders to match.
At this stage, you are not breeding for mutations yet. You are simply trying to create males and females with matching stats.
Most people select all stats so every breeder has exactly the same stats and level.
Leave Gender set to None, because you need both males and females.
Once your filters are set, use:
Activate → Prepare Dinos for Breeding → Start Breeding → Start Breeding
The Propagator will now only give you eggs that match all of the stats you selected.
This can take a little while.
Keep breeding until you have:
1 perfect male
As many perfect females as you want
The more females you use, the more eggs you produce, which gives you more chances of getting mutations.
Once you have your breeders ready, stop breeding and set up for mutations.
Breeding for Mutations
Place your perfect male and perfect females into the Propagator.
Open Filter Settings again.
Under the Mutation Filter, select the stat you want to mutate.
For example: Melee
Only select one mutation stat per Propagator.
You can now untick the boxes under the normal Stats section, as the Mutation Filter is what you are looking for.
Under Gender, select Male.
This means the Propagator will only keep male babies that have the mutation you selected.
Keeping your mutations on males makes stacking mutations much easier. When you get a new mutated male, he replaces your current breeding male and breeds with the same clean females.
Your females stay mutation-free while the mutation count builds on the male line.
Then simply keep repeating the process:
Mutated male → clean females → better mutated male → replace old male → repeat
Do this separately for each stat you want to mutate.
For more information about breeding in general, please see Breeding Pairs and Breeding Mutations.
Link Your Propagator to a Hatchery
For easier egg handling and further automation, you can link your Propagator to a B+ Hatchery. Eggs will automatically be sent to the linked Hatchery.
See Linking a Propagator to a Hatchery on the B+ Hatchery page for the setup steps.