If you're using alchemy, you can pay trainer merchants for training and sell them potions to get your money back(with the merchant perk in speech). You can get to level 90 smithing in vanilla Skyrim with Eorland in Whiterun. If you have Dawnguard, Gunmar at Fort Dawnguard is a master smithing trainer and merchant.
with patch 1.9, you can make any level 100 skill legendary. This resets the skill to 15 and refunds any perk points spent in the skill. You can then raise the skill again for more xp to level up your character. You can make a skill legendary as much as you want, removing the previous level cap of 81 and allowing you to get as many perk points and attribute increases as you want.This is most easily done(without exploits) with Alteration(telekinesis fast traveling between Markarth and Riften) and Illusion(cast Harmony in a crowded place like the Riften market during the day. May help to be thane wherever you try this so the guards don't get on your back). One of the Black Books on Solstheim ( Dragonborn DLC) has a power called Secret of Arcana. This lets you cast spells with zero magicka for 30 seconds each day. Works well for the telekinesis trick(if you are doing a constant cast when the power runs out, you keep casting for free) and can work with the illusion trick if the place is crowded enough and you have buffs to magic xp skill gain. This can be helped with the Aetherial Crown from the Dawnguard DLC(store Lover stone in crown, get Mage stone as regular, sleep with a spouse while the crown is unequipped for 15% bonus and then put on the crown. Total 50% bonus to skill xp using mage skills). A really crowded place is the basement of the Blue Palace in Solitude after winning the civil war for the Stormcloak side.
The point for the original poster is that you can get the smithing skill high(90) without using the skill and spending perks. Then, combine it with several fortify smithing enchants(probably only three, but up to 25% each) and a smithing potion(combine high skill and perks in alchemy with say 3 25% alchemy enchants) and the combination of your raw smithing skill(sans relative perk), enchants(bought or looted) and potion(crafted with the help of bought or looted enchants) should allow you to make anything legendary.
In addition to the atronach forge, another reliable source of daedric weapons and armor is the Dremora Merchant. He can be accessed by using the Black Market power from one of the Black Books in the Dragonborn DLC(forget which book atm).