the point of that compound is to verify you have a full seat between the valve and seat. it doesnt seat the valve.

your shop should be doing this.

i just got done finishing my own heads, i work at a machine shop.

the process is, grinding the seats, to the angle specification, being your valves are new you wont need to grind the valves.

you shop will lap in the seats with the compound to verify the valves seat completely.