Generally, the hardest process to master without a lathe is reducing the tip diameter flush to the ferrule without damaging the ferrule. Here's a method to try if you have an electric drill available: I have two sanding discs that chuck in my drill, one with 100 grit and one with 320. I wrap the ferrule with one layer of automotive pinstripe tape(about.010 thick) and one layer of masking tape in a contrasting color before gluing the tip. Once the glue is set, I clamp my drill to the workbench and lock the trigger on. Rotate the ferrule against the 100 grit disc, keeping it perpendicular to the sanding disc until you're just about thru the masking tape. Remove the masking tape, and switch to the 320 disc. Repeat the procedure, removing just enough leather until you can start to see the white of the ferrule through the striping tape. Then clamp the shaft horizontally to a workbench between some soft rubber vise jaws. Cut some 1/2 inch wide strips of 600, 1500 and 2500 wet-or-dry sandpaper. Wet the 600, drape it over the tip, and pull it back and forth shoeshine-style. Rotate 1/4 turn and repeat just until the tape has been sanded away at the tip/ferrule seam. Remove what's left of the tape, and repeat the procedure with 1500 and 2500 to polish the tip and ferrule. Finally, turn the paper over and burnish with the backside of the paper with the same procedure until everything's dry. After a little practice, you'll have a smooth, shiny tip that is perfectly flush with the ferrule, as well as a polished ferrule. I defy anyone to tell one of my tip jobs apart from a lathe-trimmed tip. It took longer to type this than it normally takes me to do a tip. Maybe when my kids come home from college later this month I get their webcam and do a video. Another benefit of this method is that you'll never delaminate a tip from trimming.
Bill