TRT absolutely will not work if you have low SHBG. It is impossible.
If you have low SHBG, and you are secondary, your testosterone is low because your body is already making the maximum amount of testosterone that it can handle in lieu of the low SHBG. Pardon me for exploding for a moment: but if you add testosterone in this scenario then you are a fucking moron. Adding testosterone when your body cannot handle it makes absolutely no sense.
Notice, however, that I said TRT and not HRT. Solutions for this scenario are to be found in repairing SHBG expression by alleviating the causes through lowering cortisol, correcting insulin resistance and correcting any adrenal abnormality (excess, in particular.) You may be absolutely screwed, however, as low SHBG can be congenital. It's the male version of PCOS. Luckily, all women have to do is take anti-androgens. We currently have no idea what males should do.
You have to understand that your low testosterone is a SIDE EFFECT OF ANOTHER PROBLEM. It is NOT the problem you should be aiming to solve. Your body has no problem producing testosterone. Your body has no problem expressing LH to "ask" the testes for testosterone. Your body does not WANT any extra, because it cannot properly metabolize any extra.
You will not find a single member of this board who successfully treated a low SHBG by using extra testosterone. Any "relief" will be transient. There are a number of doctors that will be clueless about this, including Dr. Scally, so beware.
If you did experience some benefit, it could be that your low SHBG is simply a side effect of driving your estrogen so low and that you do not have naturally low SHBG. In that case, you're one of the lucky ones.