1. What can I use for seals for irregularly shaped air gaps and spaces?

You can use more than one type of weatherstripping or seals for irregularly shaped air-gaps, spaces etc. Some common types of weatherstripping: tension seal, Self-stick plastic (vinyl) folded along length in a V-shape or a springy bronze strip (also copper, aluminum, and stainless steel) shaped to bridge gaps in windows and door rails, stiles and sills; The shape of the material creates a seal by pressing against the sides of a crack to block air gaps, and drafts.
Inside the track of a double-hung or sliding window, top and sides of door. Surfaces must be flat and smooth for vinyl. Can be difficult to install, as corners must be snug. Bronze must be nailed in place (every three inches or so) - Do Not Bend or Wrinkle. Can increase resistance in opening and closing doors and windows which may not be a good thing if you have back problems. Self-adhesive vinyl is also available.