I am going to chime in here a bit as I have been employed in the Boston area building restoration trade for many years...I started off for 25 as a bricklayer but now everything is steel, glass and caulking and we have restored just about all the brick in the city it seems or covered it up...There are some amazing and very applicable technologies we use and I would like to suggest you look at them...caulking is quite simple actually in choice...Tremco DyMonic(Amazon has listings for it)...with a tenacious level of adhesion and flexibility you could almost seal the door hinge with, it is an amazing sealing product with the best of both silicone and polyurethane as well as like I said a tenacious "stick"...bear in mind this is a serious amount of stick so make sure you wont be taking this off in a year...if you look at most buildings made of stone panels you will see the caulked joint and this is the stuff most often used.
I have recently purchased a 92 Contessa Signet and it was fraught with leaks I have traced to the gutter seal mating sides and roof as well as some awning rivets and gutters...I removed said gutters and put a dymonic seal in there and then some on the gutter back and added all new SS fastners and no more leaks...I resealed all the pocket marker lights(added LED's too).
When we do caulking we tool the joint as well with a slicker which most would recognize as a sort of frosting knife...its rounded on the end and sized to make the appropriate profile width desired...bigger joint bigger slicker...thats how we get that very even concave profile...not a finger...
ROof leaks can also be easily handled with dymonic but we did do a serious gash from a branch in a friends trailer with a German product we used ALL over Fenway Park and Boston Symphony called Kemper...if you have a real need I can explain that on demand but though it is expensive it is almost utterly indestructible as well.
I mentioned rivets above as well and those times when you need to replace them I encourage you to look to the aerospace industry for them...I use MONOBOLT rivets exclusively as they do not have a nail in them but a splined spreader that far exceeds most other pop rivet type designs...they are not gennerally capable of being drawn by a hand rivet gun unless it is a hand/hydraulic...
lastly finding leaks can be challenging but you have to think a bit more like rain...we make a simple soaker rack from HD/Lowes PVC parts...get oil burner nozzels...about 3 and pvc pipe bits to make a row of 3 nozzles coming out at a right angle to the pipe (cross and some 3 way unions and short bit of pipe 3/4" diameter and adhesive...ask or find threaeded adapter for nozzles)...add a handle if necessary with a pipe hanger and some threaded rod...you now have a water broom you can use to irrigate suspected areas with a more concentrated rain like flow...
