No sir, dewaxed shellac is the universal basecoat. It is what makes Kilz brand primer work.So you'll start with Timbermate, and then seal that with shellac? Any problems with enamel (e.g. Rustoleum) over the shellac?
My house is used. The people that lived here before somehow got oil or grease all over the walls in the kitchen and dining room.
I sprayed the walls in those areas with kilz primer, when I ran out of kilz, I used dewaxed shellac. They both worked.
Zinser sanding sealer is just 2 pound cut dewaxed shellac.
Zinser shellac is 4 pound cut normal shellac.
Shellac is made from the secretions of the Lac bug. It is used in candy, food, and wood finishing.
Check out youtube on Shellac and a process called French Polish. It is a giant rabbit hole. Very cool stuff.
Below is a French Polish Shellac Finish I made for my wife.