I have created a simple language that compiles to brainfuck which can be found here: http://code.google.com/p/brainfuck-compiler. There is a compiler for the language implemented in java.
I use the following function in that language to output a number. Maybe you can analyze the generated code and see if anything can be of use to you from it. One word of warning though, it does generate a bit of redundant copying around of cells (never got around to optimizing this). Anyway here's an example program and the BF code it generates. (note that indentations MUST be tabs in my language)
declare n, 165
declare digits
while n
push n % 10
digits = digits + 1
n = n / 10
if digits
while digits
out pop + 48
digits = digits - 1
else
outs "0"
And here is the generated code for that:
>>>>>>>>>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++[<+>-]<[>>+>+<<<-]>>>[<<<+>>>-]<[[-]<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-
]++++++++++<[>>+>+<<<-]>>>[<<<+>>>-]<[>+<-]>[<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-]<[>+
<<-[>>[-]>+<<<-]>>>[<<<+>>>-]<[<-[<<->>[-]]+>-]<-]<<+>]<[>>+<<-]>>[<<<[>+>+<<-]>
>[<<+>>-]>-]<<[<<->>-]<[-]<[>>>>>>>>+<<<<<<<<-]>>>>>>>>>[>>]+[<<]>[>[>>]<+<[<<]>
-]<<<<<<<<<<[>>+>+<<<-]>>>[<<<+>>>-]+[<+>-]<<<[-]>>[<<+>>-]<<<[>>>+>+<<<<-]>>>>[
<<<<+>>>>-]++++++++++<[>>+<<-]>>[<[>>+>+<<<-]>>>[<<<+>>>-]<[>+<<-[>>[-]>+<<<-]>>
>[<<<+>>>-]<[<-[<<<->>>[-]]+>-]<-]<<<+>>]<[-]<<<<[-]>>>[<<<+>>>-]<<<[>>>+>+<<<<-
]>>>>[<<<<+>>>>-]<[<+>-]<]<[>+>+<<-]>>[<<+>>-]<[>+<[-]]+>[<[-]<[>>>+>+<<<<-]>>>>
[<<<<+>>>>-]<[[-]>>>>>>>>[>>]<[<[<<]<<<<<+>>>>>>>[>>]<-]<-<<[<<]<<<<<>++++++++++
++++++++++++++++++++++++++++++++++++++[<+>-]<.[-]<<<<[>>>>+>+<<<<<-]>>>>>[<<<<<+
>>>>>-]+[<->-]<<<<<[-]>>>>[<<<<+>>>>-]<<<<[>>>>+>+<<<<<-]>>>>>[<<<<<+>>>>>-]<[<+
>-]<]<[-]]<[>>++++++[<++++++++>-]<.[-]<[-]]<[-]<[-]>>>>>>>>>>>>[>[-]>]<<[-<<]<<<
<<<<<<<<<<<<<<[-]<[-]