More years ago than I like to admit, but like to brag about, Edwal fixer concentrate came with a suggestion that you add fixer concentrate directly to the used developer, using both in one-shot manner. I have found that this also works with TF4. You need enouugh head space, if you using a tank, to hold 1/16 of the amount of developer, so you may have to pour out a little developer. This trick comes in handy sometimes when you're on the road and want to see some results before you leave the scene. You carry a tank, a bottle of developer concentrate, a bottle of fixer concentrate and a graduate.
Needless to say, you agitate vigorously after adding the fixer to the developer to get thorough and rapid mixing.