What's the secret to posing?

Head Control!

How you grab the rabbit's head and the angle of pressure that you apply can drastically change the way that the hindquarter sets up. At no point should you be putting straight downward pressure on their head. You should be firmly holding the head in a 45° angle, slightly lifting and then putting pressure back towards their elbows. A majority of the adjustments should be coming from the hindquarter after that.

Stop pushing your rabbit's chin flat to the table!! Not only are you going to make the shoulders look excessively long and angular but you're also pulling the hindquarter forward and naturally distorting the peak placement.

Thumb position is important. Not flat with your hand and not wrapped behind the ears. You want to be gripping their head with thumb wrapped around to some capacity.

Posing is more than just feet placement

The goal of posing is to not only have the rabbits feet correctly placed, but to adjust the rabbits body such that the weight transfer is directly over the hindquarter. If the rabbit is pushing or pulling back then the weight is not centered on the hindquarter.

Struggles?

Difficulty posing can be due to structural problems but if you're new to posing it's less likely the rabbit because even rabbits with structural issues can be posed by expert posers. So it's more like the worse the fault the more difficult to pose, not impossible to pose

Can you train a rabbit to pose easier?

A tame rabbit can make it easier to pose but they can also be manhandled with confidence so don't feel like if you don't practice daily then you're rabbits will be harder or impossible to pose. Oftentimes, between the ages of 6 weeks and 16 weeks, I have only posed our rabbits maybe 5 times for 15 seconds per session. Practice is not always required for the rabbit, but it absolutely is for the person!

Compact Vs Commercial Posing

There is no difference. The reason compact bodies and commercial bodies SHOULD look different is because of the way the body is structured. The technique for posing is the same. You should never intentionally elongate a commercial rabbit. If a Rex looks like a compact body type is because it was bred that way - not because of posing.