I have never used a sliding scale for anything - yet. . .
I figured out my Lantus dose by specifically testing to "measure" how much basal insulin I need. Basal needs testing is simply a day of fasting with regular (every 1 or 2 hours) BG testing. Without food intake, your BG should remain fairly stable over the time. If it drifts up, you need more basal, downward drift means less basal.
Whatever Lantus dose changes you make, I think you should give the change a chance to have a consistent effect before changing again. Make a change, check the results over 3-4 days, then decide whether another change is needed.
I also split my Lantus dose, morning & evening. There's a fair amount of experience on this forum & elsewhere indicating that Lantus doesn't last 24 hours for everybody, so doubling the number of shots (which is not a problem for me) ensures that I don't have to deal with that problem