For the first part, set the KeyPressFcn property of the GUI figure window. Enter docsearch('figure properties') and scroll about a third of the way down, to the end of the section on KeyPressFcn, to see an example of detecting and acting on a ctrl-p action.
I don't really understand the second part. Changing any property is done using set(handle,'PropertyName',value). This can be done in a callback, so it occurs in response to a user action. The figure's KeyPressFcn callback could also call a callback like this, so the action is mirrored in a keyboard shortcut as well as a uicontrol action (like pushing a button).