I used three different applications to post to Instagram. The native S-Note application, PicCollage and Photogrid. But most of the collage were designed using PicCollage hence I find that tool the most useful for the job.
Posting to facebook directly has it's own merit based on the picture quality. Instagram seems to degrade and pixelize the rendered image. Regardless, I exported to Instangram beside the quality loss since it would automatically post to Twitter and Facebook automatically. Don't judge me but yes I am lazy.
Here are the pictures