You can use Far Manager with k300 with no problem at all. I used cruiser cable and Far Manager with SEFP plugin in order to complete phone after flashing with setool. I used Far Manager instead of "complete phone" form setool because I wanted to do a error free customization. Error free means that no 1E0W (1 error 0 warning) would appear at software information on phone menu.
So, you need a T28 service cable or a cruiser cable. Data cable will not work with this, since pin configuration on old sonyericsson are different for data cable and for service cable.