We love our open fire. We have a friend that owns an enormous piece of land and we have logs from him, plus logs from my dad. Some burn better than others.
We haven't 'properly' weathered ours at all, they're just stacked at the back on pallets. We brings piles in every other day and store then in the cupboard under the stairs to dry out a little, sometimes not at all by the time they are needed. We use a good selection: twigs to start it off followed by some smaller logs/larger twigs. Only once its really going do we put the larger logs on, or the damp ones.
I wouldn't worry about burning painted wood so long as your chimney is clean, free and clear. I would think twice about something other than general emulsion though!
I'm interested in having a log burner but I'm reluctant to use it in place of the open fire. It's difficult to move the dog from in front of the fire in the winter, we have to stack logs around him, and I don't know that he would be happy if we replaced it
Someone I once knew had a wood burner installed and she loved it, she collected drift from the beach and used that.