Riordan, who scored a brace in Saturday's SPL win at Falkirk, opened the scoring against Brechin with an exquisite chip 10 minutes in.
His cross was then deflected into the net off Ian Nimmo before Hanlon struck from 25 yards shortly after half-time.
Neil Janczyk missed Brechin's best opportunity as former Easter Road boss Jim Duffy endured an unhappy return to his old club.
It was also a bad night for new Hibs striker Anthony Stokes, who wasted a host of chances to open his account.
Manager John Hughes had vowed to field a strong line-up in a bid to aoid the sort of upset predecessor Mixu Paatelainen suffered against Morton a year ago.
But he still made four changes, including handing goalkeeper Graham Stack his debut.
Irn-Bru Second Division Brechin drafted in Nimmo and also recalled the fit-again Janczyk.
Hibs fielded a three-pronged attack, with Riordan and the recalled Abdessalam Benjelloun flanking Stokes.
Stokes and Riordan combined inside five minutes, the latter making space in the box before chipping left-footed over the bar.
Riordan then dragged wide from 20 yards from a stray Brechin pass before opening the scoring superbly in the 10th minute.
Stokes fed the forward from the left flank and this time Riordan made no mistake with the chip, his right-foot effort sailing over a stranded Craig Nelson.
Gary Fusco gave Hibs a scare when he almost bundled his way through but it was soon 2-0.
Nelson turned Stokes' low near-post drive behind, Riordan played a short corner and his cross took a deflection off Nimmo which left the goalkeeper helpless.
Janczyk could have pulled one back after ticking his way into the area but he lifted his finish over Stack and just past the post.
Stokes then wasted two great chances, shooting narrowly wide after being put clean through before slicing horribly on the rebound after John Rankin's 20-yard curler had hit the upright.
Riordan lashed an angled volley over the bar as he sought a first-half hat-trick.
Moments before the interval, Benjelloun cut inside and drilled just wide left-footed, while Rankin failed to find the target from 10 yards.
Riordan smashed a left-foot volley from Rankin's corner over the bar shortly after the restart.
The striker would have been proud to score Hibs' third goal, which arrived in the unlikely shape of Hanlon 10 minutes into the half.
The left-back cut inside 25 yards out before arrowing a right-foot shot across Nelson and into the corner of the net.
Stokes missed his latest chance from a Riordan corner, but the duo were combining well, the latter's cross almost finding his team-mate six yards out.
With the game up, Brechin brought on Chris McGroarty for Nimmo, while Hibs handed a debut to highly-rated striker Kurtis Byrne, who replaced Benjelloun.
There was more woe for Stokes when he poked the ball too close to Nelson, shortly after Brechin had replaced Charlie King with Ian Harty.
Hibs then withdrew Rankin for Lewis Stevenson before the luckless Stokes finally appeared to find the target with a vicious volley, only to see it blocked.
Hughes threw on a fourth striker in Colin Nish only to see Stokes, Byrne and the substitute all miss chances to score a fourth goal.