We made lined curtains for our boler
which keep light out nicely. We also put film on the windows
(purchased from home depot as a kit with spreader, squirt bottle and liquid and cutter)
If you follow the instructions carefully, its not too bad to install. Just make sure you use a lot of the spray liquid, or it may stick to itself and render itself useless. Been there, done that!
Practice on the smallest window -- save curved windows
for when you get the hang of it.
The best part of the film, is that people can't see inside, as its reflective. At night though, if you have lights
on inside, then folks can see through. This can be a little embarassing if you didn't know!