Some time ago at the other place I asked how you would translate - you use your bare hands (said as a command)
CaoimhínSF gave me - bain feidhm as do láimh nochta
and Fiairefeadha gave me - bain feidhm as deis do lámh
I was wondering whether in the second phrase should it be - láimh - or not?

It should be lámh, as given in this case.

for
you use your bare hands (said as a command)
I'd say something like
Déan le do dhá láimh féin é!

_________________
Bí cinnte de go nglacfaidh triúr le gach aistriúchán a thabharfar.
Be sure to get three in agreement with a translation given.

The nominative plural of lámh is lámha.
After "dhá" as Braoin wrote, you use the dative form: láimh, so dhá láimh.

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Go raibh maith agaibh