You can go back and scrape off or peel the left over membrane from the hide Brennan, but whether or not the tanning chemicals of the Lutan F you used was able to penetrate around that and get through the skin, I can't tell ya.
Removing the untannable protiens such as the membrane, fat and/or whatever else you have left on there WILL help to soften the hide yes. But for future reference as I'm sure you know, the hides need to be fleshed clean...literally...before any tanning begins.
Tumbling the hide will HELP
Tumbling in sawdust will HELP
Stretching and working the hide will HELP
...but none of these will be a cure if any of the debris left on the hide prevented the tanning chemicals from doing there job, ya know what I'm sayin?
Future advice for removing the membrane you say?
There's lotsa ways... /ubbthreads/images/graemlins/wink.gif
-Salt your hides till they dry first.
-Pickle them in a tanning acid with a P.H. level of 2.0 or lower for 72 hour minimum.
-Wash the greasy hides in a good tanning degreaser so it lets you at the membrane.
-Put a little acid bate in your pickling solutions.
-Be sure your using a good fleshing knife and beam your comfortable with.
-Get yourself a fleshing wheel.