You can increase your blood volume with cardiovascular exercise which will lead to a lower hematocrit. It sounds counter intuitive but is usually highly effective. So effective in fact that exercise induced anemia is fairly common because it.
You can also make sure you are keeping your test levels in "normal" ranges (ie 600-800) instead of the normal 800-1000 or higher that most people on TRT seem to prefer...
As stated above, blood donations are the standard way (always whole, never double, double puts your platelets back, you want the platelets gone, that is what makes blood "sticky").
Personally I think most people will stabilize at safe levels without donations unless they have a blood disorder or are taking too much.