How do I make a hotkey that changes a property?

Question

In my addon (Blender 2.8) I would like to have a hotkey that changes the value of a Property (to be exact: a BoolProperty which is a part of a PropertyGroup). I have found a way of doing this for an Operator, but I can't figure it out for the Property.

Properties are mentioned as a possible space_type for new keymaps, but it wasn't enough info to get me going. How can I achieve this?

The code I have right now does not work (i.e. the hotkey 1 is not executed):

import bpy
class FP_PT_user_panel(bpy.types.Panel):
    bl_idname = "FP_PT_user_panel"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"
    bl_label = "Test Prop"
def draw(self, context):
    layout = self.layout
    col = layout.column(align=True)
    col.prop(context.scene.brush_properties, 'is_smooth_brush', text='[1]Smooth brush', toggle=True, icon="BRUSH_SMOOTH")



class BrushProperties(bpy.types.PropertyGroup):
    def smooth_brush_handler(mod, context):
        # some other stuff here #
    for a in [a for a in bpy.context.screen.areas if a.type == 'VIEW_3D']:
        a.tag_redraw()

is_smooth_brush: bpy.props.BoolProperty(default=False, update=smooth_brush_handler)



addon_keymaps = []
classes = (
    FP_PT_user_panel,
    BrushProperties,
)
def register():
    for cls in classes:
        bpy.utils.register_class(cls)
bpy.types.Scene.brush_properties = bpy.props.PointerProperty(type=BrushProperties)

kcfg = bpy.context.window_manager.keyconfigs.addon
if kcfg:
    km = kcfg.keymaps.new(name='3D View', space_type='VIEW_3D')
    items = []
    addon_keymaps.append((km, items))
    kmi = km.keymap_items.new("wm.context_toggle", type='ONE', value='PRESS')
    kmi.properties.data_path = "scene.brush_properties.is_smooth_brush"
    items.append(kmi)



def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
km, items = addon_keymaps.pop()
for i in items:
    km.keymap_items.remove(i)
addon_keymaps.clear()

del bpy.types.Scene.brush_properties



if name == "main":
    register()