I think 2,400 is small compared to Google but it doesn't mean its useless. Remarketing is more about audience quality than just size. If those people already visited your site or showed interest, even a smaller audience can bring good results. With Bing the volume will always be lower, so you probably wont get the same daily impressions like Google. I would not put a big budget on it at first, just run a small test and watch metrics like conversions, CPA and frequency. If the audience is too limited, you can also expand the window (like 60-90 days) or combine similar audiences if available. I would still keep search campaigns as the main focus and use remarketing as an extra layer.