Hehe, when i train i simply start in versus mode with a non combatant as fiend.
Just run around and see if you can shuffle around, with fox nairing more than 8 times in a row usually becomes exceptionally straining in my case.
I like to train long wavedashes, Waveshines(I usually mess up with Illusions and stuff -_-), wavelanding, and ofc the simple shorthops and SHL/SHDL's.
Anyhow i'm sure you can do atleast one shuffle in the silence and depth without screwing up ;P
Try to do another one right after. L-canceling should come naturally(I do it with R)
Simply I try to hit R each time i touch the ground, except when i wanna flubb a tech on purpose.
My advice would be to focus less on comboing and working hard on making shuffles and rightfully wavedashes something natural. When you master those aspects you can often move on to comboing, though its hard with link
Once you get the sence for l-canceling all attacks on ground it should be piece a pie to l-cancel 100% of the time. Even with other characters ^^
There are though some abillities which feel strange why L-canceling and the timing becomes weird with them, like falcon Dair, Fox Dair, Marth dair et.c
But i'm not an exceptional player at melee so dont take my tips for granted, just how i do.