what thing/material to prevent solder go over neighbor

[abdulbadii]

How to solder tiny, tight, narrow pinhole and PCB layout, what thing/material to prevent solder to go over neighboring pin/hole ?
Of course, means it must be little/non heat conductive to prevent draining soldering iron heat

[coromonadalix]

you could use Kapton tape or what we call  "peel off"  its made for electronics, its a kind of semi liquid foam  (heat resistant solder resistant)  you mask the things you dont want to be touched .... it will dry in 15-30 mins, do the job you want to do   and after you can peel it off 

you have some who can be washed off  ... it will desintegrate with water