Playing the leadpipe isn’t the same as the horn, nor is buzzing the mouthpiece or free buzzing.
If possible, I would try to bring your horn with a practice mute or something.
But if that’s just not possible, then the leadpipe and mouthpiece and going through WindWorks courses is probably your best bet.
Remember that playing isn’t not about muscular development as much as it is about coordination. There are great players who have taken a lot longer than 12 days off the horn and come back and hit double C’s without a warm up.
There’s a lot of WindWorks that you can do away from the horn. So much of playing is mental.