Public transport is pretty good in the Netherlands. Website 9292.nl can help you plan your trip. Basically, you need to find the train to Venlo. Then catch Bus 377 to Castle de Berckt in Baarlo. The bus platform at the train station is where your weekend starts as it is unlikely that you are the only one on that Thursday afternoon trying to get to the Castle. We can already sing baldy hash songs on the bus if the driver is in a good mood. From the De Berckt bus stop it is a short walk to the Castle. The bus ride takes just 17 minutes, but the frequency is only once an hour in August. Ask the bus driver to tell you where to get out.
Train rides are a pleasure in itself. Bring your own picnic with beer or wine and enjoy the trip. Bringing booze could come in especially handy if you arrive at the Castle before 16.00 when the bars open.
You pay for your trip with an OV-chipcard. This card is valid for all public transport in NL. If you don't have such a pre-payd card, you can buy tickets from the bus-driver. Train tickets are for sale at machines and ticket-booths at the larger train stations. You cannot pay cash. We Dutch prefer debit-cards (credit-cards are not very popular over here) but credit-cards should work as well.
Be smart and take into account the time you need to get to the venue from these airports on Thursday as well as the time needed to get back to the airport on Sunday. Arriving late on the Thursday evening and leaving before breakfast on Sunday is not smart hashing at all. Consider booking extra nights before and/or after the event. RyanAir is cheap, but connections suck most of the time.
Schiphol Airport Amsterdam
Schiphol is fully integrated with a main train station. Trains to Venlo depart every 30 minutes, you may need to change trains, 9292.nl will tell you where and when - It is 2 hours + 10 minutes to Venlo. In Venlo, you take the bus to the Castle.
It is well connected to Venlo. Buses depart every 30 minutes for a 20-minute ride to Eindhoven Central Train Station. From there, direct trains to Venlo depart every 30 minutes - It is a 40 minute train ride to Venlo. In Venlo, you take the bus to the Castle.
Maastricht - Aachen Airport - It says Aachen but it is Maastricht in the Netherlands
Bus 30 departs every 30 minutes to bring you from the terminal to Maastricht Train Station. From there you take trains for 1 hour to Venlo. In Venlo, you take the bus to the Castle.
Ryanair - Dusseldorf - Brings you to Weeze Airport, which is not Dusseldorf at all.
It is not far away, but public transport sucks. Book a taxi or shuttle from this airport. Try to arrange that they bring you to the venue instead of dropping you off at the Venlo Train Station (Venlo Train Station is the default destination for airport shuttles).
Dusseldorf Airport - Fair warning, this is not the airport Ryanair uses. Ryanair uses Weeze Airport.
It is not far away, but public transport sucks. Perhaps best to book a taxi or airport shuttle. Try to arrange that they bring you to the venue instead of dropping you off at the Venlo Train Station (Venlo Train Station is the default destination for airport shuttles).