How to create effects that encase objects?

How can I create effects that cling to and encase objects. My game plan is for a 3D environment, I am using Unity 5.3, and I have 2 separate scenarios in mind:

1. If I were to make a gun that shoots tar continuously, what is a resource friendly way of the tar clinging to every static and dynamic object it comes in contact with? I was thinking of using a particle effect, and having the oldest particles being deleted after a maximum particle limit is met, or suitable in game tool can remove them, but I am not sure how to have the effect stick to things and be effected by physics. I would also like the effect to be intractable, like the tar slowing movement, or being slippery.

2. How can I create an effect, whether its slime, magic, water, etc, that completely encases its target as well as any objects they're wearing or holding (like clothing or weapons)? I'm not sure tagging would be enough, because let's say I shoot a freeze spell at a person, and if the spell hits their clothing, it's effects wouldn't reach the person. The best example I could find online similar to what I would like to create, is from the link below: https://www.youtube.com/watch?v=tdlSRu0NFU4 ~Frost: 24 seconds in ~Slime: 40 seconds in. Or an even better example, the coder from the next video is able to accomplish what I seek for both static and dynamic gameobjects: https://www.youtube.com/watch?v=aDht3p5Gr3M

I appreciate any insight anyone can provide to accomplish the above 2 effects.