Yeah they did look pretty clean didn't they? Obvious they had access to a shower! I like the scene too and the toothbrush was the clincher sticking out of Ennis' mouth!
They've always looked freshly scrubbed even on the mountain minding 'em sheep. I don't think there was any dirt on 'em cowboys not even when they were wrestling the sheep after the hail storm.
Ennis, on the other hand, after the summer of '63, working on the road, on the ranch, started to get dirty, his hands started to get all kinds of scars. Jack was pretty as always, the rodeo cowboy. I don't know if Ang Lee did that on purpose, or if Heath did that himself. I suspect the two of them collaborated on the littlest detail to add authenticity. Ennis was always the perfect cowboy on that mountain, but life and poverty wore him down, just as surely as the life separated and love denied wore down Jack.
What I like the most in this scene is the extreme happiness that one can perceive in Ennis delicious abstraction of everything what is surrounding him; the greatest example of this is the phrase "He's from Texas",when Alma is asking if his friend would have a cup of coffee. 
However,I think that Ang wants to show us that never happiness is complete,to compare this just found with the one they had in BBM;they're the same,their love is the same,but their circomstances aren't already.And for this,he shows this happiness of theirs as an obstacle for Alma's own,so we see her crying and feeling alone; and,somehow,her happiness is also an obstacle for theirs,even if we see later that she wasn't the main problem really...
I love the happiness in Ennis in this here scene as well, just as much as the happiness between him and Jack, just before Acquierre spied them with his binoculars. Ennis was horseplaying with Jack, grabbing his shirt and running off, then allowing Jack to catch him and wrestle him to the ground, both half naked. Those were the happiest, most unguarded moments when the innocent child in Ennis comes out to play. Alma was probably more hurt by the fact that she had never seen her husband so happy, except on their honeymoon in the snow. The betrayal is hurtful enough, but to see that a strange man can make him more happy more than she could...
To top it all off, she probably remembered about the postcard, and what Ennis said, ...fishing buddies....twang...that music is brutal.
He is from Texas...there goes our Ennis with his sense of humor...Jack would have laughed it off. Alma just didn't get it..."Texans don't drink coffee?" The script writers are genius, too. The disconnect between them is now as complete as it gets...divorce is only a matter of time.
In a way, the toothbrush was an instrument of anticipation for Ennis, of good times; for Alma, it was an instrument of destruction, of her marriage, hope and dreams going out that door with the cowboy and the shiny new red truck.
