Some of my gymnasts are practicing exactly the same things. Both skills are a bit scary and some kids who has the strength and everything struggle with them.
I love drilling skills and this is my best advice:
BHC:
1) Have you ever tried it with rope /BHCmachine around you and the bar? It helps you to learn how to lean back, stay hollow and shift your wrists without bending elbows. It also helps with timing and saves your spotters hands.
I couldn't find a video that shows the rope back hip circle but there is one about front hip circle:
Ask Al Fong - Dragon Gymnastics [url]www.gagecenter.com: The Front Hip Circle - A rope, a sneeze, and a good old fashioned hand spot ---your choice of teaching aids![/URL]
It's the last video on that page. You can see how the gymnast is "tied" using a rope.
2) Take a piece of PVC bar and stand on soft mat with it. Hold the bar like you actually were doing a back hip circle. Remember, hollow body! Then fall on your back. Make sure you stay at the exactly same position all the time and don't pike!
3) Place a soft mat under the bar. Do a big cast, lean backwards when your hips is about to touch the bar (not your belly!) and then loose the bar and land on your back onto the soft mat. You may need a spotter making sure you ungrip at right time and don't hit the bar by feet. This drill has helped some of my gymnast to find out that going backwards is not scary but fun. Most of them had a trouble that they waited too long after cast and THEN tried to go over the bar.
There is a video about what I'm talking about:
Free HIp Circle Tutorial Video - Gymnastics Instruction - YouTube Look at 2.07. Notice that this gymnast is doing this drill for FREE hip circle so she doesn't touch the bar by her hips.
SQUAT ON:
1) Get comfortable jumping on the bar. Use floor bar a lot and do at least 100 reps
2) Place a soft mat under the bar. Use a minitramp jumping on the bar, then jump off and land on soft mat.
3) Use a spotter a lot. She makes you feel more comfortable and takes care you don't miss the feet and land on your face.