Hi. I assume that your deck drains connect to hoses which run down inside the hull then exit via a through hull closer to the waterline? These are not cockpit
drains - which are of course a safety
issue if they get blocked. The whole purpose of deck drains being to avoid getting vertical dirt stains down your topsides where the water would otherwise drain off your deck via scuppers or gaps in your toerail?? So they are purely cosmetic & a couple of thoughts occur: first, you need to make certain those deck drain hoses are secure & substantial otherwise you have potential sea water leaks
off your deck & into your boat in strong weather
. Next, if you cut holes in your toerail you defeat the object of having deck drains - they are not there to drain your deck (scuppers do a much better job of that) but to avoid topside stains. Last - where is all that dirt coming from? presumably leaf litter from nearby trees when you are on the hard? Why not put a tarpaulin over your deck instead? otherwise, the sink or shower
drain screens sound like a good idea.