That’s a little harder to offer a swim to than a corn snake. 
But yes, I have used oil too in the past, I preferred olive oil. Either end as you say, depending.
Got to be careful by mouth that it goes deep enough so it doesn’t end up in the lungs.
@emac13 (if your not experienced at this, probably better to get a specialist vet to do it.)
If they are feeding, I also find the method of defrosting the food item in water which gives maximum water and maximum hydration, that helps avoid dehydration complications in some snakes.
But we do not have this information, which could make all the differance.