Idiom-Request – Idiomatic Way to Say ‘Hide Your Lips’

Looking at this from his perspective sounds good to me. You could also say

• putting yourself in his position
• looking at it through his eyes.

If you really want an idiom, in addition to putting yourself in his shoes, you could try walking a mile in his shoes:

walk a mile in (someone's) shoes
To spend time trying to consider or understand another person's perspectives, experiences, or motivations before making a judgment about them. I know that certain people can come across as selfish or mean-spirited, but you should try walking a mile in their shoes before you dismiss them too quickly.

First of all, there would be nothing wrong with using "Let's roll up our shirt sleeves," even if the workers were shirtless. That has become a figurative expression, not a literal one, and rarely are actual shirt sleeves rolled up when people say it. That said, the idiom seems to mean, "Let's get underway," more so that in means, "Let's work hard." I think hard work is implied, but this isn't really something you say to people who have already started working.

One idiomatic expression I can think of would be:

Let's put some elbow grease into it!

I like how American Heritage defines elbow grease (emphasis added):

elbow grease

Strenuous physical effort, as in You'll have to use some elbow grease to get the house painted in time. This term alludes to vigorous use of one's arm in cleaning, polishing, or the like. It soon was extended to any kind of hard work, and Anthony Trollope used it still more figuratively (Thackeray, 1874): "Forethought is the elbow-grease which a novelist ... requires."