I used optimol paste on a side not I cleaned up the Keihan systen with a wirox disk on a grinder came up like new ,im not sure what grade stainless they use bit mine had a few cracks and corosion on it having said that I have no idea how old the system is and I think the bike had a hard life in the past as it was propper filthy and every bearing needed changing.
I am a cheapskate as well, I mix copper slip with graphite and paint the exhaust threads, the copper slip burns off leaving the graphite in the threads, the graphite is from a joiners pencil, works for this tight arse!