Finland is a member of the Schengen area, so travelling to Finland from inside of the Schengen area is very easy.
From the Ministry of Foreign Affairs, you will find information on from which countries you will need a visa and travel documents approved by Finland, and much more: http://formin.finland.fi/public/default.aspx?nodeid=49153&contentlan=2&culture=en-US
Find out more about Finland here: http://www.visitfinland.fi/en/
Find out more about Juupajoki and travelling to there from here: https://www.juupajoki.fi/kuntainfo/municipality-of-juupajoki
The closest and most suitable airport is Tampere Airport
There are domestic flights to Tampere from Helsinki-Vantaa
Importing an Airsoft gun to Finland does not require a separate permit, but may require a separate guncase depending on the airline. It is good to be in contact with your airline in advance and to reserve time at airports if the authorities want to check your game equipment. If you fly through other countries, make sure to check the laws of the countries about airsoft guns.
The easiest way to fly is to Tampere Airport, from where you can reach Juupajoki by train in about 40 minutes. The price of a train ticket from Tampere is about 3.5 € / way. Check vr.fi for prices and schedules.
You can also travel to Finland by boat. The main ports are Turku, Helsinki and Vaasa.
It is best to come by car from Vaasa.
Juupajoki is located between Tampere and Jyväskylä with good road connections.
When travelling by car, you need an European registration plate or a country tag.
If you are bringing a special vehicle, please check with the regulations/legislation concerning it.
You can rent a car for your trip from almost everywhere in Finland. When you arrive by plane, you can also rent a car from most of the airports.
Make sure your car is insured.
By train you travel comfortably to Juupajoki, from where taxi connections take you to Juupavaara in less than 20 minutes. The Juupajoki stop is located on the Tampere – Haapamäki trainline, which is commuted 4 times a day.
Check the car-carriages from vr website.
Juupajoki is a small municipality in Finland. The town is located in Pirkanmaa region. Despite its small size, Juupajoki offers all the services you need from your stay. For more information on the area, visit Travelling in the heart of finland website.
Finnish august can be somewhat warm even up to + 20 °C during the day but also cold days when temperatures are only about 12°C are possible. Cold nights were temperatures to drop from + 5 to + 10 °C, which is aggravated by fog and moisture. So book a warm sleeping bag and clothes for cold nights. Autumn average temperatures.
The sun starts to set after 22:30. The sun rises after 04.30. The nights are really bright, but you should still take for example a headlight with you.
In august, heavy rains / thunderstorms may also occur in Finland during hot summers, which may take a few minutes to hours or then only occur in smaller rains. So take with you your rain equipment, just a rain cover may not be enough in wet woods.