But the movement feels identical to when I am lifting the 10kg bar. Maybe I should just try lifting the olympic bar again (thought last time I did that, it aggravated that hip injury a bit)?
No, I reckon your hips just weren't used to moving.
I don't have access to any resistance bands, which sucks as a lot of mwod's exercises use them.
What about box squatting? If there's a box of appropriate height I could use that?
again, yes in principle, but no in practice. Box squats are great for helping filters get their technique right and tuning their strength, but it won't really help beginners.
Mobility work:
Hips
Mwod hip opener
http://www.youtube.com/watch?v=JBHzXF-mVjY
Not sure if I'm doing it right though, his videos are quite difficult for me to follow. According to that vid, I should feel it a lot in my abductors, but I feel it more in my adductors.
good. This is probably why you have a 'hip injury': your glutes and accessory muscles (like piriformis) are probably very tight. To get your adductors lighting up, push your knee out a it more and repeat the stretch.
Also I do lateral lunges which icecold recommended which seem to work quite nicely.
Hamstrings
Just a good ole bend down and try to touch your toes. Is that a good hamstring stretch? I'm not actually sure.
Great for stretching your back. Sngle leg groiners here. If you're determined to do a static stretch, sit on the floor with your leg straight in front, keep your back straight and get your knee to your nose. Keep your pelvis, lumbar and thoracic spine rigid by bracing your core and forcing your hips to move... To what you see in the gym which is all lumbar flexion and pointless.
Glutes
No mobility work yet for glutes, will work that in.
Sit on a hockey ball and try not to scream.
I don't have a specific before video, but I do have this video from a couple of weeks back
http://www.youtube.com/watch?v=WrvuJWtUfj8