have got bogged down on these whole red chilli.
there is a video on youtube explaining the rehydration. simple stuff really needs no instruction. however it states there can be bitterness. lost the link and would appreciate if chrisnw could re point to it. you dont think much of the idea of bitterness during the video but it hits you full on when you make.
nearest youtube ive found (red chilli sauce)
https://www.youtube.com/watch?v=a4Lgl-IsaN84 off whole chilli rehydrated in 100 ml then blended and used in 1 off portion madras. also tried removing the water whilst hot and blending in watered puree (seems a tad better but no breakthrough)

ps forgot to add - these whole long chilli "kashmiri" are very different to the crushed red chilli. they are less hot and have more flavour. feel you need to keep both.