If you have a leak around the gaskets you must stop riding the bike . The pressure from the cylinder will push into the radiator and force out the coolant , you will damage your pistons as your bike will overheat . You will get a false reading on the temp gauge as there will be no coolant for the sensor to read and you think the bike is running cool while it is over heating . Strip the heads and barrels , check both sides to make sure they are perfectly flat on plate glass . If not , rub them down . Use blue marker to highlight any problem areas . Refit and look for bubbles in the radiator while the bike is running , bubbles are bad .
About the sealant , some swear by it while others swear about it . Use some grease on the base gaskets so that they don't stick as much to the casings .