You really shouldnt use fabric softener though since it gives a finish to the fabric that repels water - not the best thing in towels.In lieu of a handy tumble dryer ( and Im presuming you dont have one otherwise you would have tried that )white vinegar added to the final rinse is (supposed to be ) a fabric softener.Worth a go anyway.
i always have soft towels, but that is because i tumble dry them (i use bounce in the tumble drier, but no fabric softener in the wash), they always get crispy on the line. when i didn't have a tumble drier for a few months my hatred of crispy towels got to the point where i was taking them to the local launderette rather than wash them at home.
i understood what you meant, if my reply doesnt fit round yours it's because we posted at the same time (there were no answers when i started typing....you know how it happens) :-)
Treaclefight is right a tumble dryer gives you really soft towels. If you want to dry them outside then just give them 5 minutes in the dryer when they are nearly ready .. that is enough to soften them.