A couple of thoughts come to mind:
1. All your 3 cent locomotive stamps will be 114, period. Some may have a split or double grill, true.
2. Do not remove the stamps from the covers no matter how tempted you are. The value on-cover will (almost) always be more for the complete piece of postal history than any soaked-off stamp.
The best way I find to see grills is with side lighting at an extreme low angle. Consider this scan of a cover and its stamp with direct head-on lighting from a scanner. It shows very little grill detail:
Not a satisfactory view of the grill at all. But when viewed at a low angle with a bright light also at a low angle looking into the light like this ...
one can rotate the cover around to get the best shadow effect of the rows and columns of the grill. I did a set-up like this in a dark room:
And then can take a photo straight-on with the side-lighting at the best angle - in this case at about the 3:00 position.
And the grill shows up quite well - even when not professionally exposed for true color. Of course there is no need to try to photograph the grill, just that low angle light is your friend.