Hi Rizzini. Kranks have an exellent choice of all things black powder related. Plenty of choice in the gun department and helpfull with advice.
As far as black powder v pyrodex v 777 goes i dont know anyone who can shoot bp who uses anything else. I have four bp guns and have never found cleaning to be an issue, evan when left dirty for a few days. 10 mins with hot soapy water or consentrated screen wash, rod out the barrel, cylinder ect and dry with a hair dryer. Lube with any decent gun oil an stick it in the cupboard. My nitro firing long barrel revolver gets just as cruddy and takes just as long to clean but admittedly it wont rust if left.