Please advise:
I am not yet soloing after returning to the hobby. Instead of buying an ARF/RTF Superstar and the like, I built my very old 3-channel kit of a Cessna 172. I built it accurate and straight. Since the front gear is not steerable, I was hand-launching it. another thing, it is a little small and has a slightly high wing loading (22-23 oz/in^2). It usually flies well - but I still have hard time hand-launching it. Last week it was the second time that it crashed immediately after takeoff[&o]. It hit the grass at just above the launch speed - straight down.
As with the first time, there is absolutely no sign of damage (the fuselage is made of thick flexible plastic). Even the engine is protected by a thick plastic cowl - but now that a little lump of dirt made it to the entrance of my LA-25 carb, there was a risk that little rocks would make it inside. I removed the plug , pushed some fuel into the cylinder and genty rotated the crank so that the fuel sprinkled out of the carb. I did it three times.
My questions:
1. Take off: How should I hand launch this beast without ever crashing (reminder : relatively small (51""), no ailerons, high wing loading)?
2. Did the method above for flushing the engine suffice? I would prefer to avoid removing the carb on this new engine unless it is essential for cleaning. But I want to avoid grinding the engine with one or more soil particles that may make it to the combustion chamber.

Because of time constraints I did not add ailerons (for improved roll control immediately after launch) or steerable nose gear (for ROG).