Hi francdore
I used needle files for ages, incorporating a handy rounded homemade jig used with fine sandpaper for the final crowning
I would file a pyramid shape to the fret, then using the jig, run through 1000, 1200, 1500 paper (wrapped around the jig) to create a perfect crown.
The jig I made with a piece of aluminium, using a round needle file to create the concave rounded edge.
This really works, but takes a bit of time. If you're not doing a lot of necks, then this would save you a lot of money. 8)
I only just bought an offset diamond fret file from stewmac ($99 before shipping and vat), cos the amount of fretwork I do now requires a much faster production line.
Give it a go, unless you have "splodges of whonga" (as Bob would say) ?