There are a lot of things to consider when painting a picture of this size. The problem with a big picture is that with pastel pencils you have a small pencil and a big canvas area to work. If you are right handed you work from left to right and down.
If you are doing a landscape and have quite a large sky, you can imagine with a small pencil, this will take some time to do. You could use Polychromos Pastel Sticks to cover large areas but I would not choose to do this myself. Polychromos are a bit brighter than pastel pencils so whatever you put over the top i.e. trees, animals etc will not look as bright. You could end up having a sky that stands out too much! The same principle applies with soft pastels.
When I did my Polperro Harbour picture using Pastel Pencils, there were times I was using 3 or 4 fingers to blend. That picture was done on mount board with Ingres Pastel Paper on top which was quite thick. When it comes to framing this kind of sized picture, I’d recommend getting it stuck onto a large board. I double mounted my picture and put a little slip inside (almost like having 2 or 3 mount boards stuck together). This pushes the mount away from the glass and means there is a gap of about 3/4 cm and the pastel cannot touch the surface. There is always the option to fix your picture but as readers know, I don’t recommend doing this as it can make the picture look dull.
Have you painted A2/A1 sized pictures? Let us know your experiences in the comments below.