Install a Barton shifter bracket first. I doubt fluid will cause such a big problem. Barton Industries Mustang Shifter Bracket - MT-82 2011BM-4 (11-14 GT, V6) - Free Shipping 2011BM-4
The problem is that isn't really possible lately. To get into 2nd I have to perfectly rev match, and 3rd feels like I'm chipping teeth or something.
2014 Mustang V6 3.7L 6-spd manual, with MGW shifter, Airaid CAI, BBK shorty headers, Corsa Sport axle back, strut tower brace, JLT oil separator, GT500 differential cover, BG Synchro Shift II gear oil, Redline differential oil.