Accessing and changing Custom Property through "prop()" in Custom UI Python

Does anybody happen to know how to access and change the Custom Property using “prop()” for purposes of editing using a custom UI within python?

These are the custom properties I wanted to change:

And I thought this python code would do the trick:

import bpy

class LayoutDemoPanel(bpy.types.Panel):
	"""Creates a Panel in the scene context of the properties editor"""
	bl_label = "Test"
	bl_category = "Panel"
	bl_space_type = 'VIEW_3D'
	bl_region_type = 'TOOLS'
	bl_context = 'posemode'

	def draw(self, context):
		layout = self.layout
		scene = context.scene
		ob = context.object

		row = layout.row(align=0)
		row.alignment = 'CENTER'
		col = row.column()
		#rna_item = context.space_data.pin_id
		col.prop(ob, "Arm_Left_FK/IK")

When I hit run script, there is no Slider Created to allow me to change the property from within my custom-made User Interface. So once again, any idea on how the custom property can be accessed using “prop()” within python? Thanks!