One of the most important parts of getting a good, long lasting gel coat spray job is using the correct catalyst ratio, on these guns the ratio is a guess at best, you really have no clue as to how much catalyst is being dispensed compared to the gel coat.
Can it work, yes, but it can be very inconsistent, to the point of complete failure.
Older, full sized gel coat spray equipment used a similar system, but it had several different adjustments that could be made to meter the catalyst flow, including a sight gauge that sort indicated what the flow might be. On these old units you needed to calibrate the gun before using it each time, some companies did it several times a day, others not at all. There are none of these old type pressure tank systems on the market anymore, they all went to a slave arm mechanism for a much more accurate and repeatable catalyst ratio.
Many years ago Binks came out with the same type of catalyst spray tip for their small siphon and pressure pots, it didn't catch on because of the same issue, no real control of catalyst ratio.
