I dump the fractions one at a time into the flask to combine them and just make sure to rub the rim of the test tube on the edge of the flask I am transferring to for 2-3 seconds. To get the remaining traces of solution, I'll put all the tubes back into the rack and squirt a little liquid into the first tube, then transfer that liquid tube to tube until I reach my last fraction, then add that to the flask.
You just have to be patient (which for most chemists I think is asking for a lot, myself included).