We are preparing to shellac-prime all of the walls on a rental house due to nicotine odors. Is it best to apply this product with a roller or airless sprayer?
Shellac/alcohol based primers like Bulls Eye work great for sealing stains and odors in many applications, however they do put out a lot of alcohol fumes. Spraying increases the amount of volatile gases in the air and should only be used in a very well ventilated area and with proper protective respirators. You can actually get very intoxicated, legally drunk from hours of exposure. There is always a risk of fire or explosion if a large concentration of alcohol fumes are exposed to an open flame or hot spark, so be very careful.
I have dealt with the identical problem of neutralizing smoking odors in an apartment. I believe you will have equal success using a good latex/water based primer. A water based primer is easier and safer to use, and I'm sure you will see good results. Because to the large areas you need to seal, I'd recommend avoiding shellac and go with latex.
Water-based primers just don't always do the trick, but when using a Shellac based primer such as Rustoleum BIN primer, I suggest rolling it on. I sprayed a full interior the other day (which I regret 100%). It was awful, and I was extremely intoxicated for longer than just that day due to the fumes. My boss sent me in with this product and had no knowledge of the Shellac base. I guess I was over trusting. It is an unsafe to spray this product without extreme ventilation and proper respiratory gear. All I was wearing was a NIOSH N95 respirator and consequently breathed a lot of it in. As well, the filters on the respirator are permanently saturated with ethanol.