Welcome to Holy Black. In a traditional, loose powder is the way to go. Your 2F should do well, you might want to try 3F, especially if you're using a smaller than .50. As mentioned, Pyrodex is not a good choice in a flintlock unless you're prepared to use a duplex charge. But, if you're going to buy Black in order to do that, why complicate things? On that note, if you do have a flintlock, you don't HAVE to use 4F for priming. Pyrodex is reported to lose effectiveness, over time, once the can is opened. If it's just for plinking, it'll likely serve you well for that. As to which is more corrosive, there's some dispute regardless, they both produce corrosive fouling and need to be properly cleaned ASAP when you're done. Plain WARM (not hot) water with maybe a bit of Dawn soap works as well as anything for cleaning.
Myself, I scrub out the barrel, run a dry patch or two through, WD-40 to deal with any water not absorbed by the patches, dry patch and then oil with Break Free. WD is not designed as a rust preventative although it may work to an extent. Some folks swear by Bore Butter for that, some swear at it. Different folks, different strokes.
What kind of Muzzleloader do you have? Do you know the twist rate? 1 in 48 is the most common in modern ones like a Hawken or Lyman Plains Rifle but other twists may be encountered. This will affect what type of projectile will work best, slower twists work better for round ball. 1 in 48 is a good compromise that works well for all bullets, just maybe not the optimum for any particular style.
Check out blackpowderrifleaccuracy and order a copy of Dutch’s system. He’s a great guy and has forgotten more than most people will ever learn. He can be found on Traditional Muzzleloading Forum as well. Send cash, postal money orders don’t work when he tries to cash them and for some reason Canadians can’t use a credit card. When corresponding use large font, capitals or even bold type. He's having the dickens of a time reading with very poor eyesight. Haven't had a chance to try it out yet myself, got it late last year and the range is still snowed in but lots of very satisfied customers.
As far as shooting supplies, I’ve yet to find a truly great online supplier in Canada. Hillfolks in Saskatchewan seems to be well regarded but last time I checked they weren’t online. I have purchased from Track Of The Wolf and The Gun Works (in Springfield, Oregon) and can recommend both. Rustywood in Mission seems to be a good supplier of powder, never shopped with them.
Make good smoke.
