Use a Solar Recombinator
Your sun has everything you need to get full-sized oceans in 10 to 100 years.
Finding, capturing comets and bombarding your carefully terraformed planet seems expensive and hazardous and way, way too time consuming. Plus it's too unpredictable. You need a systematic, reliable, predictable process.
Better would be to use technology to extract the oxygen and hydrogen that your planet's sun already has in abundance. Assuming your sun is within the main sequence, it lacks the core pressure to fuse Oxygen, however most Suns are composed of about 1% Oxygen (from previously exploded Suns) which is WAY more than you need. Of course, the Sun is 98% Hydrogen with the remainder being Helium which is being fused in the core....
Anyway - The easiest place to find Oxygen in the Sun is within the Sun spots which are cool enough (4500K) to collect it in its molecular form. Given this, the solution needs three primary subsystems:
Solar Oxygen Extractor - This would be a solar satellite which
orbits the Sun and can be directed to pass over Sun spots where it
could collect the O and using magnetic resonance (think rail gun)
shoot a beam of O atoms to an H2O Recombinator that is permanently
located at your planet's L1 Lagrange point (the one between the sun
and your planet.) Depending on the flow you need, you could have many of these.
Solar Hydrogen Extractor - Like the O extractor, the H extractor
orbits the Sun, collects the Hydrogen, and shoots a beam of H to the
H2O Recombinator. You will have have twice as many of these as Oxygen extractors (e.g. H2O).
H2O Recombinator -- This is a massive space station, with two
receiving pads -- one for the O and one for the H. Within it, it
maintains a continuous combination reaction to create water. Once created, the water is immediately sprayed in a long beam (via Ion
wave transport) at very high speed towards your planet. The beam of water
in the vacuum of space will immediately crystallize, but it will not
have time to sublimate before it hits the upper atmosphere where it
will immediately melt and add to your water cycle. Because the
recombinator station is at L1, your planet will be rotating in place without any relative motion, thus the ice beam will create a nice even coating of moisture throughout your world without any need to for hyper accurate aim
corrections for timing, etc. -- EASY! Let the oceans naturally form in the low altitude regions.
In order to create 10^18 tons of water (which is how much the earth has) over a period of 100 years, you would need to send water at the rate of about 300 million tons per second. (And you think comets could get you there? no way!) This seems incredibly high, but its not if you build a large enough recombinator.
Assuming the size of the water dispenser on the recombinator is roughly a 1000m x 1000m square (or 1 million square meters), you only need to produce an ice stream 300 meters long per second -- which is certainly do-able as long as the inputs coming from the solar extractors have sufficient flow rates.
If 100 years is too slow, you can make it less than 10 years if you just ramp up the flow rates or deploy additional recombinator stations.