HI Ivan, welcome to the wonderful world of podiatry :)
You will find various practitioners use various techniques to cast, and everyone has there opinion as what works best.
At uni i was taught the suspension technique with the patient supine, an apply pressure to the 4th and 5th met heads, thereby locking the MTJ and moving the entire foot to the position you felt was neutral (with the other hand on the head of the talus). This allowed you to see if tib ant fired which would dorsiflex the first ray, and be detrimental in orthoses manufacture. This is the technique i used throughout uni.
However, when i began work arfter uni, I found i felt i had a better visualisation of the foot with the person prone and looking down at the posterior aspect of the foot. This is the best way to identify Forefoot to rearfoot alignment, and therefore i feel the best wat to have maximal control over the foot as you cast. If tib ant fires, I believe you can feel it, and see the first ray elevate, so this is not a worry to me. I feel i get a far better cast this way.
In regards to how many methods I know in weightbearing, I choose not to use weightbearing as i feel you will not get the good results you can get when casting non-weightbearing. If you are casting a patient, they will have have biomechanical abnormality, hence why you are seeing them (duh!??!!). IF you cast them while standing, you are capturing them with abnormal posture, whereas non-weightbearing you can manipulte the foot (must be careful with that word
) to a postion you see as biomechanically corrected.
Holding the foot in neutral while weightbearing i find difficult, as you will find the first ray will nearly always dorsiflex, which will again be ineffective when made into an orthotic device.
This is obviously my opinion Ivan, and im sure with casting a few times you will find what works for you.