Did it with my Cleric too (he's 41 now). Now to be clear, I randomly joined a Cazic Thule group once, and got an entire level in
well under half the time it would have taken me to get solo. In other words, just to be clear, soloing as a Cleric is very much
not the fastest way to get a high level Cleric!
But, if you're like me and just want a more interesting solo challenge, solo Cleric can be a lot of fun. If you can afford it I'd recommend a Fungi and a Velium Crystal Staff (and maybe an FBSS or SCHW) to speed up the low levels, but beyond that twinking won't do a ton for a Cleric (of coure, 6/65 rings and similar gear certainly won't
hurt). Oh, and also one of those Braziers of elemental summoning can make the early levels fly by (I love using those to "PL" all my new toons to 10 or so).
As for a leveling path, if you want to follow mine the
https://wiki.project1999.com/Per-Level_Hunting_Guide (click Cleric at the top) actually has a decent one up to 40 or so. Basically you start with scarecrows in WK, move on to Lake Rathe (at night) and Rathe Mountains (during the day), and then head over to Tower of Frozen Shadow and do its first two levels.
You cold keep doing ToFS, but CRs on the third level up are a giant PITA (heck even level 2 is super annoying unless you have an alt parked nearby to help get you the key). I'm now exploring City of Mist, but I want to go back to TT and try the undead soon (at 41 they were blue, but too high to solo). If anyone has any other good level 41 suggestions I'd love to hear them.