I've been using one of my favourite modelling materials to fill in the gaps in the corners of the windows on 121.
Milliput - the two part epoxy putty produced by a family firm in Gwynedd - is ideal because it is firm enough that you can push it into small spaces without it squirting out the other side as some of the stuff you get from a tube would.
At the same time you can add a droplet of water to it and make it run into tiny gaps and afterwards wipe away any excess.
Whilst it does take 24 hours to set the benefit is it remains workable for a long time so it doesn't develop a fragile skin within a few minutes of contact with air, and it also dries to a perfectly smooth finish which can be sanded, drilled or filed.
Later on it the project it will be my material of choice for forming the domed ends on the roof.
Sometimes I wonder how I would ever manage without having some of it in my modelling box.