Photoshop’s Vanishing Point can push the grids back into your document. Make a new white-filled layer that is set to Multiply Mode empty layer before you head into Vanishing Point. In VP, check out the drop-down menu in the upper left-hand corner (it’s tiny). Turn on Render Grids to Photoshop, draw your grids, and hit OK. Now you have grids on their own layer. It will save you a LOT of time when matching type to box faces or other perspective-y things.

 



When you have something you wanna liquefy, get it on its own layer, or a merged layer with everything.
(Use The Claw [Command+Shift+Option+E/Ctrl+Shift+Alt+E])
and then Image>Image size>[something smaller here, but still big enough to see properly];
then Liquefy, and when you’re done, before you hit okSave Mesh and Cancel.
Step back in history to just before you resized.
Filter>LiquefyLoad MeshOK.
This will let you work on a lower res image (faster in Liquefy’s private memory space) and also allow you to use much larger brush sizes relative to the image. I always save right before I run heavy duty filters like Liquefy, in case of a crash.
The combination of these two things will let you use grids of any size inside Liquefy. Resize your file, Vanishing Point yourself some grids on a new layer, do your Liquefy, (Save Mesh and Cancel), step back a couple of steps in History, make sure you’re on the right layer, run Liquefy (Load Mesh, OK) and there you are.
This all sounds like a giant pain in the ass, but it’s actually very fast.

|| Thanks to +Dennis Dunbar for pointing out that VP can draw grids on a blank layer. I thought it had to be filled with pixels. He’s got a good tutorial on grids-from-VP here: http://www.dunbardigital.com/blog/blog.php?id=381721930900789741