So I downloaded a couple of CLDC and they were extremely hard. Even if I slowed the song down a lot it was near impossible. Is there a way to search to find learning CLDC or am I back to buying official DLC?

theres alot of different CDLC for learning, They are usually listed under the artist "You" or "Lessons". Other than that find easy songs to play to learn from and get better.

The second topic under this one :

You Exercises : The RS14 Collection (Standardized)

Try downloading some of the easy song from this list.

https://docs.google.com/spreadsheets/d/1HzgY90kLwyGqzJ-R64v8lmpeQMMhhxwGwUlenepIgms/edit#gid=7

I Mainly Play Bass but today dusted off my LES PAUL 6-String Guitar and enjoyed some White Stripes...

a Few of my Customs have been easy as to play...

for example: 

 

https://www.youtube.com/watch?v=Q4_a7F9ysP0

 

Played it on My Yamaha PSS 290 SYNTHESISER  - She Wants Revenge - Tear You Apart

 

Played using 80s Yamaha PortaSound Synthesiser (PSS 290)

 

Using dual Tones on the Synth it-self :  "BASS PICKED" + "BASS SYNTH" for most realistic sound + Same In-game Tone as I like to use with my Yamaha RBX270 4-String BASS...

 

It's An Easy Song... only 4 Notes from memory...

Also... i used to always start the game with Korn - 4U

 

26 Notes for 100% ... All Long Sustains... Good Basic Practise...

 

Also Stuff like:

Marilyn Manson - The Nobodies

Nirvana - Sappy

Nine Inch Nails - Just Like You Imagined

 

Eminem Tracks for eg are usually just one Bass line... on repeat...

 

Even if you only have a 6-String... i recommend trying out the Bass Emulation... 

 

at least that way you can practise using 2/3 of your instrument without so many Chords everywhere...

You should be able to play the Pentatonic scale, in different ways.

and for the chords, F-Major barré kind of chords combined with C, G, Am.

 

These are essential, basic. 

Once you master them, so many customs will become playable at 80 to 90% speed.

You can find such exercices in the link given by Firekorn.

You can also add Dynamic Difficulty to most CDLCs if they don't have it already using the Rocksmith Toolkit. I do that on occasion if I start a song and am like "whoa, yeah that's not happening..." also, Riff Repeater is your best friend.

Dynamic Difficulty is bullshit, (except for fast unregular repetitions of chords in rhythm parts) just my honest opinion.

Why learn a broken series of notes, when at the end they have all to be learned one after the other..

Better off to slow the real thing in Riffrepeater, even speed 1 for very fast arpeggios or solos