Loading a muzzleloading shotgun is similar to loading your rifle but there are differences:
After the powder, an overpowder card, and a cushion wad is loaded, then the loose shot, followed by an overshot card - more steps than a rifle with a patched ball. The cards & wad below the shot and the card over the shot will need to be placed with the ramrod as two separate actions. Some shooters use just 1/2 of a cushion wad. There are a number of methods for lubing the wads, just as there are for lubing patches. The cards and wads are available in large packs from places like Track of the Wolf, etc. and come in many sizes as not all guns are bored to the same exact dimensions.
RE shooting shot from a rifled barrel, it can be done but the rifling tends to spin the shot into a donut like pattern which as might be imagined, is not an effective way to shoot shot.
There are many individual preferences and "tricks" to loading and shooting a shotgun but I have tried to stick to the basics. If you do a search of past topics on the Forum, you will see a number of loading tips and discussions re attempts to shoot shot from a rifled barrel.