On my 3d profiles I get into an upright flat spin by:
Climbing at about 60 deg with enough power to continue climbing - apply full left rudder
Apply full up elevator as soon as it responds to rudder
Add right aileron as required
You may need more throttle. Too much aileron may roll it out.
This gets my planes spinning without violent contortions during the transition.

To do an inverted spin:
Climb at 60 deg inverted, apply right rudder.
Apply full down.
Ease in right aileron, throttle as required.