I am very new to all this but found that there are functions in the core library's that will 'format' a number and make a string.
Since strings are arrays, using dtostrf (DoubleToString formatted) you can go from 123.456 to ,,,[.],,,[\0] in 1 step.
float iVarToCast = 123.456;
dtostrf(iVarToCast, 7, 0, buffer);
dtostrf(YourNumber, TotalStringLength, NumberOfDecimals, TheTargetArray)
TotalStringLength > Must include all characters the '.' and the null terminator
NumberOfDecimals > The output is rounded .456 become .46 at 2 decimals
TheTargetArray > I suspect 'char strBuffer' will work with out a preceding definition but I haven't tried yet
Hope this helps