How to jungle with an ADC?

The only ADC that was ever viable for jungle in the first place was, and probably still is, Twitch. But he was never centered around efficient clearing and many jungler aren't. Ganking was his go to mechanism.

I'd recommend:

Grump(smite) -> Blue -> Wolves -> Wraith(smite)
Back
Red
Gank-> Situational

Runes:
Flat AD Reds
50/50 Flat Armor Health Yellows
1 Flat AD Quint, 2 Flat AS Quints
50/50 AS / Scaling MR or CDR Blues

Items:
Purple jungle, Devourer (Here's your clearing potential)
Standard twitch: BOTRK, Yommus, Graves, IE, def item.

A quick search on probuilds told me that some high-tier players still play it: http://www.probuilds.net/champions/Twitch

EDIT: You can actually play ranged junglers pretty well in season 5, due to the fact that you can almost completely negate buff-damage and some camps.

Released in October of 2015, Kindred are both a dedicated ranged ADC jungler. Their passive, Mark of the Kindred, marks targets to hunt:

Scoring a takedown on a marked target permanently empowers Lamb's basic attacks to deal 1.25% of her target's current health as bonus on-hit physical damage, capped at 75 (+ 10 per stack) against monsters, stacking with each Mark consumed.

As a player, you may also select one opponent champion to have as a target at any one time. This has a cooldown. The targets marked by Wolf are neutral monsters and camps. This gives you plenty of motivation to play Kindred as a jungler, build up stacks, then dominate late game.

Their Q, Dance of Arrows, has a short cooldown and hits three targets at once. It works together well with their W, Wolf's Frenzy, which lowers Q's cooldown time. It used to heal Kindred, but that was removed since Kindred was becoming too powerful as a top-laner.