My friend is clueless when it comes to modding, so basically I taught him how to use MultiMC then I send him the mods, tell him whether jar or mods folder, and he installs them simply. So far, he has had just two errors, each one basically saying that the mod couldn't find a certain Modloader method (that's from what I can tell, I'm no genius when it comes to Java). I remember one of them (with BetterToolsAndArmor Mod) was complaining that it was missing Modloader's "Modloader.addSmelting" method, the other one (Animal Bikes) I don't remember...bottom line is: Animal Bikes Mod and BetterToolsAndArmor are incompatible with Forge because of incompatibilities with Modloader.