I owned a similiar model but not HSENG AS186. It works great. No complaint about it. You should go to the supplier and try it out at his place.

It depends on which type of Mr Color paint you are using. For your information, there are 2 types of Mr Color paint in the market. The first type is the aqueous (water based) and the second lacquer. For the first type, you can use water to clean your airbrush but if you want a better solution, you can try kleenex (or whatever window cleaning liqiud in the market. If you are using the lacquer type, yes you can use Mr Hobby thinner but a cheaper alternative is the industrial thinner in hardware shop. Do take extra precaution on using those thinner though. If it is too strong, it might ruin your handpiece.

Unless your handpiece is made of plastic, it won't ruin it.

Just let the thinner run thru your AB piece and wash it thru, not by leaving them inside a bucket of thinner.