Making bars is one of the most annoying things on ironman accounts unless you get rune bars from c keys which in my opinion is not very fun. I like mining for my bars but getting the coal is a pain. There is no single npc that drops bulk coal in a decent rate. In osrs coal is not a problem for ironman since the hey the blast furnace coal shop. So my suggestion is to make coal easier to obtain in one of three ways:
1) Add coal in bulk to the ironman only shop.
2) Add coal with a decent drop rate in a decent amount to crystal demons and dragons.
3) Make mining coal faster i.e more than 1 coal per action with the possibility of the extra coal being noted (I know this is a donator feature but adding it always for coal is not a big deal).