I usually disconnect the fuel line from the fuel tank and start the engine until all the fuel in the feed line and carb are burned and the engine dies. I then open the carb and put some type of after run oil. 4-5 drops if you fly weekly, then put your finger over the carb opening and turn the prop several times. Some guys use auto transmission fluid as afterrun oil.

In answer to your engine question, I would look at what the model specifies then buy an engine on the upper end. In other words if the model calls for a .40 -.46, buy a .46. It is easier to throttle down a bit in flight and have extra power when you need it. I recall getting my trainer crossways to the runway when I was just starting, with tall weeds about 20 feet straight ahead. I punched full throttle and up elevator and was able to avoid a nasty wing puncturing experience. A .40 engine would not have provided the power I needed.

As far as what engine, most of the name brands are good. OS and Thunder Tiger are popular. I personally prefer the OS Max 46. I have flown TT with no problems too.

Good Luck and I hope you love the hobby as much as I do.

Terry