A couple of points to note that I just thought of:
Wear old clothes - I now have a pair of jeans that have waterproof knees from me getting tire sealant on them! And it won't wash out now it's dried!!
If you spill the stuff on your driveway - wash off immediately with lots of water - otherwise it leaves a permanent mark!
Keep the blue caps on the sealants at all times when not in use - otherwise the spray mech self-seals up!
Make sure the spray bottle tops stay screwed on - they have a habit of slipping loose and then you can have a spill, stain your drive, and ruin your jeans!