I've just done a Logan playthrough and I was still able to get 3 hearts with Bernard (despite curing Logan first etc). So should be possible. If I remember correctly .. First heart is meeting him at the cottage on Friday and sleeping in same bed (needs high like). Second is going to bathhouse with him, sitting near him, then looking at him so you both kiss (I think anyway) and third I'm not sure but it might the fair or when you stay overnight at his house and you two get it on. I've completed the full moon quest while focusing Logan so should be doable.