"They doesn't seem to get along much" basically means that the two Pkmn won't be having an egg for quite a while. They WILL have one eventually, but it's the longest period of time for it to happen, due to the fact that both of them probably belong to you, and are of different species. Same egg group, sure, but being different species really slows it down.
The best way of getting an egg from those two is either: getting a Ditto; or trading a Monferno/Medicham from another person. Pkmn have eggs faster if their Trainer IDs are not matched to yours... so if you were able to get both a Medicham and Monferno from two totally different people, your chances of an egg definitely increase.