hi
ive done mine this summer ... ive had to take the capping off a couple of times to get it totally waterproof

... like johnm says do two lines of dum dum, but mainly make sure they are both pretty evenly thick all the way along - i sort of smeared the sealant in well along where the runner meets the wood. you probably dont need any more dum dum except at the ends, but just stick it anywhere you think might be vulnerable, its cheap and it works .. (remember to put plenty round all the screw holes) . i agree its worth making sure all the channels are well cuprinolled and give them 3 or 4 coats of varnish, they get totally soaked . ..
the chrome just looks pretty, i used the normal stuff on the inner and the outer, its half the price.
well worth doing, my windows leaking had caused the wheel arch to rot from the inside !!

... and it gets under your back seat ...
good luck ...
grainger