Chili Colorado advice.

Looking for some tips on chili colorado if anyone has them.

Tried to make it once before but it ended up rather bitter (think I over toasted the chilies and then used the water they were soaked in to blend). I live in rural Scotland so tough to get some of the ingredients and want to make sure to get it right this time.

Have some dried ancho, guajillo and pasilla chilies, but have no experience with them so no idea on what ratios to use. Also they are all quite mild from what I understand, would it be a terrible idea to add a tsp of chili powder to the pot for a bit of heat?

Recipes I've seen usually call for mexican oregano which I haven't been able to find, I have regular mediterranean oregano and marjoram in the house, which would be best to sub in? Anything missing from the flavour of the mexican oregano that I should adjust for?

Also just any other tips and tricks you all have, anything that could help!

Plan at the moment is:

Lightly toast chilis (2 of each?) then soak in hot water for 20-30 mins, drain then add to blender with a little fresh water and blitz till smooth.

Season beef, dust with flour and fry till well browned, remove from pan and set aside.

Add 1 diced onion to pan, cook till softened then add four cloves minced garlic and 2 tsps ground cumin. Cook for further 2 mins then add chili paste. Bring to a simmer, add 2 tsp oregano and 500ml chicken stock, bring back to simmer, cover and cook, stirring occasionally for 2 hours or until meat is tender. (Add more water during cooking if stew looks too dry). Check for seasoning, might need tsp of brown sugar or honey for balance.

Seems a simple recipe but I guess the chilies are what give most of the flavour. Normally if I were making a stew I'd cook out a tbsp of tomato paste in the onions before adding anything else, would that be a good addition or frowned on in the chili colorado world?