Well I went to Physio for my hip, and on the whole I had pretty bad form.
Coming back into things I'm finding my elbows get sore getting under the bar, and I can feel that my shoulders/back have slackened
and I'm looking for pointers on what I should look/feel for to know I'm getting it right, because I feel like I'm lifting my shoulders into the bar like a shrug almost, and I don't know if that's a good or bad thing haha.
Apply the same principles as deadlifting or squatting: shoulders back and down. A "big chest" is another way of cue-ing the movement
If you think of the way your shoulders move, pressing puts tension and torque on the shoulder joint. As such, your shoulder blades, back (rhomboids, traps, lats and serratus) need to work with your rotator cuff to keep your shoulder from exploding - this happens by getting elbows under the bar, but also by bracing your shoulders (back and down).
You might want to look at your shoulder rotation (internal and external) as well as joint capsule restrictions. Then have a look at your upper back mobility, too: can you get it really straight when bracing?