Yes when you have just the tip of the rudder in the water (a couple inches), steering is a little harder than normal but not impossible, and yes you don't want to oversheet the sails. I don't furl the sail typically, it seems to work ok to just relax the sail a little, and with the daggerboard up most of the way there is some crabbing going on (side slip). But typically when I hit shallows, I didn't know about them in advance, and all I want to do is get thru them. The only other alternative is to get out and walk the boat out of the shallows (been there done that, many times, embarrassing).
I don't look at the underside of my TI very often (I typically only flip it over and repair all the gouges and scratches once a year or so). But I suspect the bottom of my TI is scratched up pretty good from running around in shallows a lot.
This might be interesting to others, annually when I flip my boat over to repair the bottom, I clean everything with a single edge razor by swiping the blade back and forth rapidly (the plastic scrapes off like snow). I then fill in any deep gouges with my Hobie welder. I then wipe down the hull with Besttest rubber cement solvent (heptane (which melts hdpe)). I then put a thin krylon clearcoat on the hull followed by Rustolium Neverwet water repellent spray, (the neverwet doesn't stick to PE, you have to have the clear coat on there first, (this applies everywhere including stickers)
This stuff.
I have no idea how much the neverwet helps, but having a clean smooth slick bottom that repels water (less friction) seems to help me get thru those shallows a little easier.
FE