Yes, always fill the TC before install. I have never heard anyone advise against it.
Obviously, you can't fill it past the half way point when you stand it on it's side or fluid will come out, so add slowly and keep checking.
97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles