Many have reported using a small dose of <a href="http://www.t-nation.com/store/products/hot-rox-extreme"target=“new”>HOT-ROX Extreme when in a mass phase to keep fat gain in check. Some like a capsule or two in the morning no matter the phase they’re in because they like the energy and mood-boosting effects. So, it’s doable.
Whether this would help you lose fat in your “slight gaining diet” is more about your food intake/choices, training, and overall plan.
I realize you’re just using up some leftover supplements, but with your seemingly opposing goals, HOT-ROX isn’t really the optimal supplement choice. Sounds like you’re primed for <a href="http://www.t-nation.com/store/products/indigo-3g"target=“new”>Indigo-3G, especially if 250g of carbs per day is a “slight gaining diet” for you. (My wife eats about that amount to stay very lean.)
If you have that big of a problem with carbs, it’s probably better to fix the underlying nutrient uptake issues with Indigo-3G. For one thing, you won’t have to sweat micromanaging food intake so much. You can stay lean (or a lose some more fat) while gaining muscle. No more “cutting” and “bulking” phases and never being truly happy with the results of either.
Consider it. Sounds like exactly what you need.