Most of the goals Barnes has scored this season have been instinctive strikes rather than pre-determined. The ones I can remember off the top are Exeter (H&A), Oldham and Posh - where he scored with a first-time effort each time. Against Orient and Bris R he controlled it but had to take a quick shot. On top of all that he's had countless efforts (mainly first time) just over the bar or past the post.
It wasn't very surprising when he had time against the Rovers GK that he failed to convert. This is the part of his game that he needs to concentrate on - getting himself composed and focused when he has time. When he gets the hang of that technique he'll be a 30+ goal man - and I doubt that he could have better tutors than our management team.
Oh, and you may have seen Bennett's comments about our front 3 where he singles out Barnes for special praise for his all-round effort - proving that it's not just about the finishing.
So, you cite in two games he controlled and took a shot, plus three penalties converted. I can't remember all his other goals, but there's five out of twelve in which he had time to think about it.