There are a few ways. The first one, is Digivolving/regressing. It seems odd, but it is definatly the best way. Every time you enter a "Form" you have not previously been, you get a higher aptitude.
Also, training using the DNA machine Farm item, will increase your aptitude by 1, but has a low percentage of doing so.
Degenerating the digimon
keep battling and digivolving and degenerating the digimon. doing so will improve its stats.
Get solarmon to level 33 with a minimum aptitude of 40 and it has to have 6000 machine exp
In order to get a Digimon's aptitude up in "Digimon World Dawn," you would have to degenerate your Digimon to a Digi-Egg.
you have to complete it first but some digimon you can only get in dusk if you are on about dawn
Degenerating the digimon
keep battling and digivolving and degenerating the digimon. doing so will improve its stats.
Get solarmon to level 33 with a minimum aptitude of 40 and it has to have 6000 machine exp
In order to get a Digimon's aptitude up in "Digimon World Dawn," you would have to degenerate your Digimon to a Digi-Egg.
you have to complete it first but some digimon you can only get in dusk if you are on about dawn
it is exogrimon
Agunimon is one of the spirit Digimon from the series. However, it is not possible to unlock him in the game Digimon Dusk.
Grimmon or Grimmon's evolution line is not obtainable in Digimon Dusk/Dawn. It is specially introduced Digimon
If you are asking about a 'Digimon Modifier' for the new Digimon Dawn/Dusk games, then no. Currently, there doesn't exist such a program, nor do I think there ever will due to Digimon's overshadowing by Pokemon. However, on the plus side, Digimon are typically easier to raise.
The Yatagaramon in Digimon World Dusk can be obtained by digivolving Peckmon. Yatagaramon is a type of bewitching bird Digimon.
ZeedMilleniummon
you don't