Leatherman,
I would recommend trying to put the tallow based finish on last because it's kind of greasy. I've played around with a tallow/neatsfoot oil combo as a finish for a bag I'm making out of veg tanned and so far I've found it works pretty good (if you do it last) to heat the tallow (mixed about 50/50 with neatsfoot oil) and when it's completely liquid brush it on with a small paintbrush. It cools quick and a lot stays on the surface so then I slick off any extra (back into the can) and use a hair dryer to warm the surface of the leather a bit so the last little bit gets absorbed in. It gives sort of a bridle leather texture (a bit waxy feeling) but I have no idea what the long term repercussions might be. Keep in mind, I haven't tried to put anything over it either.
Leatherman, I would recommend trying to put the tallow based finish on last because it's kind of greasy. I've played around with a tallow/neatsfoot oil combo as a finish for a bag I'm making out of veg tanned and so far I've found it works pretty good (if you do it last) to heat the tallow (mixed about 50/50 with neatsfoot oil) and when it's completely liquid brush it on with a small paintbrush. It cools quick and a lot stays on the surface so then I slick off any extra (back into the can) and use a hair dryer to warm the surface of the leather a bit so the last little bit gets absorbed in. It gives sort of a bridle leather texture (a bit waxy feeling) but I have no idea what the long term repercussions might be. Keep in mind, I haven't tried to put anything over it either.