Proctosol is for external use. It might be applied *slightly* internally to treat internal hemorrhoids, but never deeply enough to reach the rectal cuff. If the issue is that it’s painful to get the medicine to the rectal cuff, it doesn’t matter whether it’s cream, foam, liquid, or suppository, it would still have to pass through the anus for insertion. If the pain is simply too extreme for local treatment you could try oral mesalamine or oral steroids, and that might cleear up cuffitis for you, if you’re patient, but these oral medications (especially the steroids) have more side effects.
If *all* of your symptoms are about pain in the anal canal then I wonder if you have cuffitis at all. Do you have bleeding? Whether you have cuffitis or not, though, that local pain needs to be diagnosed and dealt with.