Here are my favorite withdrawals aids, in order of preference:
Lyrica (pregabalin) - This is a miracle, it will not only block the vast majority of withdrawal, it will make you feel awesome. I detoxed with my friend recently and we took this for a week and that week was awesome, we rented a cabin in the woods and had adventures and laughed and played music and most of the time I forgot I was even withdrawing at all. After the week we stopped taking it since it is addictive itself, and the second week was much rougher, but I was past the worst so it was bearable. It made all the difference.
Gabapentin - This is just a slightly less powerful Lyrica. It works almost as well, but produces less of its own euphoric high. Dosing 300mg every 30 minutes until you stop feeling so shitty works wonders. Both Lyrica and gabapentin work exceptionally well against light to moderate withdrawal. I have never tried them against severe withdrawal, as I didn't know about them when I've experienced very bad withdrawal. But these are amazing because, provided you don't have previous dependence to them, you can take them for 1-2 weeks and avoid dependence, and bypass opiate withdrawal for the most part.
Loperamide (immodium, anti-diarrheal meds) - This is actually an opioid (it doesn't just mimic one, it is one), which has a hard time crossing the blood brain barrier, but does in high doses. Taking the recommended dosage helps by eliminating the shits, so even its stated use on the box is a big help. But if you take a large dose, for me 40mg is the minimum but for severe withdrawal you may need to take 60mg, maybe up to 80mg, it will almost entirely block withdrawal. Some things to note, it takes 3-4 hours to really take effect so people often think it isn't working. It then lasts for about a full 24 hours. For me, it severely dries out my insides, not only constipation, but it even sometimes makes it hurt to swallow food,, like my esophagus is too dry to work properly. I always take a handful (like 10 pills) stool softeners, and eat a fiber supplement (my favorite is psyllium husk, that stuff is miraculous) when I take it. Otherwise my insides feel bad. Also, loperamide is toxic to the heart in very high dosages, so you should never exceed 80mg. Plenty of people have died from it, especially chronic high dosing. Also, keep in mind that it can produce its own dependence. it is an opiate, so it may prolong your withdrawal a bit, and if you take it too long, you will get dependent on it, and some BLers have told me that the withdrawal from it lasts for a really long time and is terrible, like methadone. Basically, loperamide is a sure thing to block most withdrawal symptoms, but it's riskier since it is an opiate itself and it is toxic in high doses. Also, it doesn't really produce any euphoria so it doesn't make you feel happy, just not miserable. Lyrica/gabapentin will help the depression a lot more, in my experience.
Kratom - This is also an opioid, though the recovery industry and places that sell it would like you to believe it isn't. It's a partial agonist of the delta and mu opioid receptors and is basically switching one addiction for another, but kratom is easier to get off of. Also if you just dose it as little as possible and stop as soon as you can stand to, you can probably escape getting dependent on it. it works pretty well to feel better, but not as well as any of the ones above, in my experience, if you are experiencing severe withdrawal. It definitely won't make you feel high, it will just make you feel more normal. Without opiate tolerance, it is a decent drug, which can sometimes be great. I started on opiates with kratom, way back in 2003. My early kratom experiences were among my most euphoric of all drug experiences, seriously they were amazing. But once I blew out my opiate receptors from years of constant kratom use and then harder opiates, I've never been able to get much from it besides a light positive feeling, and near-instant withdrawals because of the kindling effect.
Clonidine - I have actually never tried it, but people consider it a staple for withdrawal, as it basically just calms your nervous system down. Basically it calms the physical symptoms of anxiety, so it lets your body relax some. it definitely helps (apparently), but doesn't remove withdrawal by any means.