Being a portrait photographer who only shoots B&W now, I retouch every negative I print. I use an Adams Retouching Machine ( a new one- yes they still make them) but it is not necessary. You could use a light table. Also I don't believe many retouchers use pencils and retouching fluid anymore. Some retouchers use spotone but most pros I know use Veronica Cass retouching dyes(www.veronicacass.com). You use the same wet/dry brush method that you use on prints and you apply it on the front of the neg not the emulsion side.

Michael McBlane